python-intro

Python Basics
http://eueung.github.io/EL6240/py

Transcript

1. Python - An Introduction Eueung Mulyana | http://eueung.github.io/EL6240/py based on the material @Codecademy Attribution-ShareAlike CC BY-SA 1 / 121
2. Agenda 1. Python Syntax 2. Strings and Console Output 3. Conditionals and Control Flow 4. Functions 5. Lists and Dictionaries 6. Lists and Functions 7. Loops 8. Advanced Topics in Python 9. Introduction to Classes 10. File Input and Output 2 / 121
3. Agenda 1. Python Syntax 2. Strings and Console Output 3. Conditionals and Control Flow 4. Functions 5. Lists and Dictionaries 6. Lists and Functions 7. Loops 8. Advanced Topics in Python 9. Introduction to Classes 10. File Input and Output 3 / 121
4. Python Syntax Basic Types: s t r i n g , i n t , f l o a t , b o o l Function: p r i n t (python 2) Comment: # p r i n t " W e l c o m e t o P y t h o n ! " m y _ v a r i a b l e = 1 0 m y _ i n t = 7 m y _ f l o a t = 1 . 2 3 m y _ b o o l = T r u e # c h a n g e v a l u e m y _ i n t = 7 m y _ i n t = 3 p r i n t m y _ i n t 4 / 121
5. Python Syntax Note: I n d e n t a t i o n E r r o r : e x p e c t e d a n i n d e n t e d b l o c k # f i r s t d e f s p a m ( ) : e g g s = 1 2 r e t u r n e g g s p r i n t s p a m ( ) # s e c o n d d e f s p a m ( ) : e g g s = 1 2 r e t u r n e g g s p r i n t s p a m ( ) 5 / 121
6. Python Syntax Comment: # , " " " Operators: + ,- ,* ,/ ,* * ,% # s i n g l e l i n e c o m m e n t " " " t e s t m u l t i l i n e s c o m m e n t " " " a d d i t i o n = 7 2 + 2 3 s u b t r a c t i o n = 1 0 8 - 2 0 4 m u l t i p l i c a t i o n = 1 0 8 * 0 . 5 d i v i s i o n = 1 0 8 / 9 # a d d i t i o n c o u n t _ t o = 5 0 0 0 + 6 0 0 0 . 6 p r i n t c o u n t _ t o # s q u a r e , e x p o n e n t i a t i o n , t o t h e p o w e r o f e g g s = 1 0 * * 2 p r i n t e g g s # m o d u l o s p a m = 5 % 4 p r i n t s p a m # 1 , m o d u l o 6 / 121
7. Python Syntax Learned: Variables, which store values for later use Data types, such as numbers and booleans Whitespace, which separates statements Comments, which make your code easier to read Arithmetic operations, including +, -, , /, *, and % # c o m m e n t m o n t y = T r u e p y t h o n = 1 . 2 3 4 m o n t y _ p y t h o n = p y t h o n * * 2 7 / 121
8. Python Syntax Tip Calculator m e a l = 4 4 . 5 0 # 6 . 7 5 % t a x = 0 . 0 6 7 5 # 1 5 % t i p = 0 . 1 5 m e a l = m e a l + m e a l * t a x t o t a l = m e a l + m e a l * t i p p r i n t ( " % . 2 f " % t o t a l ) 8 / 121
9. Agenda 1. Python Syntax 2. Strings and Console Output 3. Conditionals and Control Flow 4. Functions 5. Lists and Dictionaries 6. Lists and Functions 7. Loops 8. Advanced Topics in Python 9. Introduction to Classes 10. File Input and Output 9 / 121
10. Strings and Console Output Assignment, Escaping Chars " M O N T Y " [ 4 ] c a e s a r = " G r a h a m " p r i n t c a e s a r # E s c a p i n g c h a r a c t e r s a b c = ' T h i s i s n \ ' t f l y i n g , t h i s i s f a l l i n g w i t h s t y l e ! ' p r i n t a b c " " " T h e s t r i n g " P Y T H O N " h a s s i x c h a r a c t e r s , n u m b e r e d 0 t o 5 , a s s h o w n b e l o w : + - - - + - - - + - - - + - - - + - - - + - - - + | P | Y | T | H | O | N | + - - - + - - - + - - - + - - - + - - - + - - - + 0 1 2 3 4 5 S o i f y o u w a n t e d " Y " , y o u c o u l d j u s t t y p e " P Y T H O N " [ 1 ] ( a l w a y s s t a r t c o u n t i n g f r o m 0 ! ) " " " f i f t h _ l e t t e r = " M O N T Y " [ 4 ] p r i n t f i f t h _ l e t t e r # Y 10 / 121
11. Strings and Console Output Functions: l e n ( ) , l o w e r ( ) , u p p e r ( ) , s t r ( ) p a r r o t = " N o r w e g i a n B l u e " p r i n t l e n ( p a r r o t ) # 1 4 # S t r i n g m e t h o d s : l e n ( ) , l o w e r ( ) , u p p e r ( ) , s t r ( ) p a r r o t = " N o r w e g i a n B l u e " p r i n t p a r r o t . l o w e r ( ) p r i n t p a r r o t . u p p e r ( ) # t o s t r i n g p i = 3 . 1 4 p r i n t s t r ( p i ) # r e v i e w m i n i s t r y = " T h e M i n i s t r y o f S i l l y W a l k s " p r i n t l e n ( m i n i s t r y ) p r i n t m i n i s t r y . u p p e r ( ) 11 / 121
12. Strings and Console Output Printing String Variables String Concatenation Functions: r a w _ i n p u t ( ) # t o s t r i n g , p r i n t i n g v a r i a b l e s , s t r i n g c o n c a t e n a t i o n p r i n t " S p a m " + " a n d " + " e g g s " p r i n t " T h e v a l u e o f p i i s a r o u n d " + 3 . 1 4 # e r r o r p r i n t " T h e v a l u e o f p i i s a r o u n d " + s t r ( 3 . 1 4 ) s t r i n g _ 1 = " C a m e l o t " s t r i n g _ 2 = " p l a c e " p r i n t " L e t ' s n o t g o t o % s . ' T i s a s i l l y % s . " % ( s t r i n g _ 1 , s t r i n g _ 2 ) # s t r i n g f o r m a t t i n g n a m e = " M i k e " p r i n t " H e l l o % s " % ( n a m e ) # s t r i n g f o r m a t t i n g , t a n d a % s d a n % # f u n g s i r a w _ i n p u t ( i n p u t d a r i k e y b o a r d p a s r u n t i m e ) n a m e = r a w _ i n p u t ( " W h a t i s y o u r n a m e ? " ) q u e s t = r a w _ i n p u t ( " W h a t i s y o u r q u e s t ? " ) c o l o r = r a w _ i n p u t ( " W h a t i s y o u r f a v o r i t e c o l o r ? " ) p r i n t " A h , s o y o u r n a m e i s % s , y o u r q u e s t i s % s , " \ " a n d y o u r f a v o r i t e c o l o r i s % s . " % ( n a m e , q u e s t , c o l o r ) 12 / 121
13. Strings and Console Output Date and Time f r o m d a t e t i m e i m p o r t d a t e t i m e n o w = d a t e t i m e . n o w ( ) p r i n t n o w # m e m b e r , b u k a n m e t h o d p r i n t n o w . y e a r p r i n t n o w . m o n t h p r i n t n o w . d a y p r i n t ' % s - % s - % s ' % ( n o w . y e a r , n o w . m o n t h , n o w . d a y ) p r i n t ' % s / % s / % s ' % ( n o w . d a y , n o w . m o n t h , n o w . y e a r ) p r i n t n o w . h o u r p r i n t n o w . m i n u t e p r i n t n o w . s e c o n d p r i n t ' % s : % s : % s ' % ( n o w . h o u r , n o w . m i n u t e , n o w . s e c o n d ) p r i n t ' % s / % s / % s % s : % s : % s ' % ( n o w . d a y , n o w . m o n t h , n o w . y e a r , n o w . h o u r , n o w . m i n u t e , n o w . s e c o n d ) 13 / 121
14. Agenda 1. Python Syntax 2. Strings and Console Output 3. Conditionals and Control Flow 4. Functions 5. Lists and Dictionaries 6. Lists and Functions 7. Loops 8. Advanced Topics in Python 9. Introduction to Classes 10. File Input and Output 14 / 121
15. Conditionals and Control Flow # r a w _ i n p u t d e f c l i n i c ( ) : p r i n t " Y o u ' v e j u s t e n t e r e d t h e c l i n i c ! " p r i n t " D o y o u t a k e t h e d o o r o n t h e l e f t o r t h e r i g h t ? " a n s w e r = r a w _ i n p u t ( " T y p e l e f t o r r i g h t a n d h i t ' E n t e r ' . " ) . l o w e r ( ) i f a n s w e r = = " l e f t " o r a n s w e r = = " l " : p r i n t " T h i s i s t h e V e r b a l A b u s e R o o m , y o u h e a p o f p a r r o t d r o p p i n g s ! " e l i f a n s w e r = = " r i g h t " o r a n s w e r = = " r " : p r i n t " O f c o u r s e t h i s i s t h e A r g u m e n t R o o m , I ' v e t o l d y o u t h a t a l r e a d y ! " e l s e : p r i n t " Y o u d i d n ' t p i c k l e f t o r r i g h t ! T r y a g a i n . " c l i n i c ( ) c l i n i c ( ) 15 / 121
16. Conditionals and Control Flow Boolean Comparisons b o o l _ o n e = T r u e # 1 7 < 3 2 8 b o o l _ t w o = T r u e # 1 0 0 = = ( 2 * 5 0 ) b o o l _ t h r e e = T r u e # 1 9 < = 1 9 b o o l _ f o u r = F a l s e # - 2 2 > = - 1 8 b o o l _ f i v e = F a l s e # 9 9 ! = ( 9 8 + 1 ) b o o l _ o n e = F a l s e # ( 2 0 - 1 0 ) > 1 5 b o o l _ t w o = F a l s e # ( 1 0 + 1 7 ) = = 3 * * 1 6 b o o l _ t h r e e = F a l s e # 1 * * 2 < = - 1 b o o l _ f o u r = T r u e # 4 0 * 4 > = - 4 b o o l _ f i v e = F a l s e # 1 0 0 ! = 1 0 * * 2 # - - - - - b o o l _ o n e = 3 < 5 # T r u e b o o l _ t w o = 3 > 5 # F a l s e b o o l _ t h r e e = 5 = = 5 # T r u e b o o l _ f o u r = 3 ! = 3 # F a l s e b o o l _ f i v e = 3 < = 3 # T r u e 16 / 121
17. Conditionals and Control Flow Operators: a n d , o r b o o l _ o n e = F a l s e a n d F a l s e b o o l _ t w o = - ( - ( - ( - 2 ) ) ) = = - 2 a n d 4 > = 1 6 * * 0 . 5 b o o l _ t h r e e = 1 9 % 4 ! = 3 0 0 / 1 0 / 1 0 a n d F a l s e b o o l _ f o u r = - ( 1 * * 2 ) < 2 * * 0 a n d 1 0 % 1 0 < = 2 0 - 1 0 * 2 b o o l _ f i v e = T r u e a n d T r u e # - - - - - b o o l _ o n e = 2 * * 3 = = 1 0 8 % 1 0 0 o r ' C l e e s e ' = = ' K i n g A r t h u r ' b o o l _ t w o = T r u e o r F a l s e b o o l _ t h r e e = 1 0 0 * * 0 . 5 > = 5 0 o r F a l s e b o o l _ f o u r = T r u e o r T r u e b o o l _ f i v e = 1 * * 1 0 0 = = 1 0 0 * * 1 o r 3 * 2 * 1 ! = 3 + 2 + 1 17 / 121
18. Conditionals and Control Flow Operators: n o t b o o l _ o n e = n o t T r u e b o o l _ t w o = n o t 3 * * 4 < 4 * * 3 b o o l _ t h r e e = n o t 1 0 % 3 < = 1 0 % 2 b o o l _ f o u r = n o t 3 * * 2 + 4 * * 2 ! = 5 * * 2 b o o l _ f i v e = n o t n o t F a l s e # - - - - - b o o l _ o n e = F a l s e o r n o t T r u e a n d T r u e b o o l _ t w o = F a l s e a n d n o t T r u e o r T r u e b o o l _ t h r e e = T r u e a n d n o t ( F a l s e o r F a l s e ) b o o l _ f o u r = n o t n o t T r u e o r F a l s e a n d n o t T r u e b o o l _ f i v e = F a l s e o r n o t ( T r u e a n d T r u e ) # - - - - - # n o t f i r s t , b e r i k u t n y a a n d , o r - - s a m a p r i o r i t a s , k l n o t n o t s a m a d e n g a n n o t ( n o t ) b o o l _ o n e = ( 2 < = 2 ) a n d " A l p h a " = = " B r a v o " 18 / 121
19. Conditionals and Control Flow Conditional Statement a n s w e r = " L e f t " i f a n s w e r = = " L e f t " : p r i n t " T h i s i s t h e V e r b a l A b u s e R o o m , y o u h e a p o f p a r r o t d r o p p i n g s ! " # W i l l t h e a b o v e p r i n t s t a t e m e n t p r i n t t o t h e c o n s o l e ? # - - - d e f u s i n g _ c o n t r o l _ o n c e ( ) : i f T r u e : r e t u r n " S u c c e s s # 1 " d e f u s i n g _ c o n t r o l _ a g a i n ( ) : i f T r u e : r e t u r n " S u c c e s s # 2 " p r i n t u s i n g _ c o n t r o l _ o n c e ( ) p r i n t u s i n g _ c o n t r o l _ a g a i n ( ) 19 / 121
20. Conditionals and Control Flow Conditional Statement # c o n d i t i o n a n s w e r = " ' T i s b u t a s c r a t c h ! " d e f b l a c k _ k n i g h t ( ) : i f a n s w e r = = " ' T i s b u t a s c r a t c h ! " : r e t u r n T r u e e l s e : r e t u r n F a l s e # M a k e s u r e t h i s r e t u r n s F a l s e d e f f r e n c h _ s o l d i e r ( ) : i f a n s w e r = = " G o a w a y , o r I s h a l l t a u n t y o u a s e c o n d t i m e ! " : r e t u r n T r u e e l s e : r e t u r n F a l s e # M a k e s u r e t h i s r e t u r n s F a l s e 20 / 121
21. Conditionals and Control Flow Conditional Statement # c o n d i t i o n d e f g r e a t e r _ l e s s _ e q u a l _ 5 ( a n s w e r ) : i f a n s w e r > 5 : r e t u r n 1 e l i f a n s w e r < 5 : r e t u r n - 1 e l s e : r e t u r n 0 p r i n t g r e a t e r _ l e s s _ e q u a l _ 5 ( 4 ) p r i n t g r e a t e r _ l e s s _ e q u a l _ 5 ( 5 ) p r i n t g r e a t e r _ l e s s _ e q u a l _ 5 ( 6 ) # r e v i e w d e f t h e _ f l y i n g _ c i r c u s ( ) : i f 5 = = 5 : # S t a r t c o d i n g h e r e ! # D o n ' t f o r g e t t o i n d e n t # t h e c o d e i n s i d e t h i s b l o c k ! r e t u r n T r u e e l i f T r u e a n d T r u e : # K e e p g o i n g h e r e . # Y o u ' l l w a n t t o a d d t h e e l s e s t a t e m e n t , t o o ! r e t u r n F a l s e e l s e : r e t u r n F a l s e 21 / 121
22. Conditionals and Control Flow PygLatin (Python Pig Latin) Ask the user to input a word in English. Make sure the user entered a valid word. Convert the word from English to Pig Latin. Display the translation result. p r i n t ' W e l c o m e t o t h e P i g L a t i n T r a n s l a t o r ! ' o r i g i n a l = r a w _ i n p u t ( " E n t e r a w o r d : " ) i f l e n ( o r i g i n a l ) > 0 a n d o r i g i n a l . i s a l p h a ( ) : p r i n t o r i g i n a l e l s e : p r i n t " e m p t y " 22 / 121
23. Conditionals and Control Flow PygLatin (Python Pig Latin) You move the first letter of the word to the end and then append the suffix 'ay'. Example: p y t h o n - > y t h o n p a y p y g = ' a y ' o r i g i n a l = r a w _ i n p u t ( ' E n t e r a w o r d : ' ) i f l e n ( o r i g i n a l ) > 0 a n d o r i g i n a l . i s a l p h a ( ) : w o r d = o r i g i n a l . l o w e r ( ) f i r s t = w o r d [ 0 ] n e w _ w o r d = w o r d + f i r s t + p y g n e w _ w o r d = n e w _ w o r d [ 1 : l e n ( n e w _ w o r d ) ] p r i n t n e w _ w o r d e l s e : p r i n t ' e m p t y ' 23 / 121
24. Agenda 1. Python Syntax 2. Strings and Console Output 3. Conditionals and Control Flow 4. Functions 5. Lists and Dictionaries 6. Lists and Functions 7. Loops 8. Advanced Topics in Python 9. Introduction to Classes 10. File Input and Output 24 / 121
25. Functions d e f t a x ( b i l l ) : " " " A d d s 8 % t a x t o a r e s t a u r a n t b i l l . " " " b i l l * = 1 . 0 8 p r i n t " W i t h t a x : % f " % b i l l r e t u r n b i l l d e f t i p ( b i l l ) : " " " A d d s 1 5 % t i p t o a r e s t a u r a n t b i l l . " " " b i l l * = 1 . 1 5 p r i n t " W i t h t i p : % f " % b i l l r e t u r n b i l l m e a l _ c o s t = 1 0 0 m e a l _ w i t h _ t a x = t a x ( m e a l _ c o s t ) m e a l _ w i t h _ t i p = t i p ( m e a l _ w i t h _ t a x ) 25 / 121
26. Functions d e f s q u a r e ( n ) : s q u a r e d = n * * 2 p r i n t " % d s q u a r e d i s % d . " % ( n , s q u a r e d ) r e t u r n s q u a r e d s q u a r e ( 1 0 ) # - - - d e f p o w e r ( b a s e , e x p o n e n t ) : # A d d y o u r p a r a m e t e r s h e r e ! r e s u l t = b a s e * * e x p o n e n t p r i n t " % d t o t h e p o w e r o f % d i s % d . " % ( b a s e , e x p o n e n t , r e s u l t ) p o w e r ( 3 7 , 4 ) # A d d y o u r a r g u m e n t s h e r e ! 26 / 121
27. Functions # F u n c t i o n s c a l l f u n c t i o n s d e f o n e _ g o o d _ t u r n ( n ) : r e t u r n n + 1 d e f d e s e r v e s _ a n o t h e r ( n ) : r e t u r n o n e _ g o o d _ t u r n ( n ) + 2 # - - - d e f s h o u t ( p h r a s e ) : i f p h r a s e = = p h r a s e . u p p e r ( ) : r e t u r n " Y O U ' R E S H O U T I N G ! " e l s e : r e t u r n " C a n y o u s p e a k u p ? " s h o u t ( " I ' M I N T E R E S T E D I N S H O U T I N G " ) # - - - d e f c u b e ( n u m b e r ) : r e t u r n n u m b e r * * 3 d e f b y _ t h r e e ( n u m b e r ) : i f n u m b e r % 3 = = 0 : r e t u r n c u b e ( n u m b e r ) e l s e : r e t u r n F a l s e 27 / 121
28. Functions Importing a Module: a module is a file that contains definitions— including variables and functions—that you can use once it is imported Math Standard Library # 1 i m p o r t m a t h p r i n t m a t h . s q r t ( 2 5 ) # 2 f r o m m a t h i m p o r t s q r t p r i n t s q r t ( 2 5 ) f r o m m a t h i m p o r t * p r i n t s q r t ( 2 5 ) # 3 i m p o r t m a t h e v e r y t h i n g = d i r ( m a t h ) # S e t s e v e r y t h i n g t o a l i s t o f t h i n g s f r o m m a t h p r i n t e v e r y t h i n g # P r i n t s ' e m a l l ! " " " [ ' _ _ d o c _ _ ' , ' _ _ n a m e _ _ ' , ' _ _ p a c k a g e _ _ ' , ' a c o s ' , ' a c o s h ' , ' a s i n ' , ' a s i n h ' , ' a t a n ' , ' a t a n 2 ' , ' a t a n h ' , ' c e i l ' , ' c o p y s i g n ' , " " " 28 / 121
29. Functions Math * a r g s : one or more arguments Functions: m a x , m i n , a b s d e f b i g g e s t _ n u m b e r ( * a r g s ) : p r i n t m a x ( a r g s ) r e t u r n m a x ( a r g s ) d e f s m a l l e s t _ n u m b e r ( * a r g s ) : p r i n t m i n ( a r g s ) r e t u r n m i n ( a r g s ) d e f d i s t a n c e _ f r o m _ z e r o ( a r g ) : p r i n t a b s ( a r g ) r e t u r n a b s ( a r g ) b i g g e s t _ n u m b e r ( - 1 0 , - 5 , 5 , 1 0 ) s m a l l e s t _ n u m b e r ( - 1 0 , - 5 , 5 , 1 0 ) d i s t a n c e _ f r o m _ z e r o ( - 1 0 ) # - - - m a x i m u m = m a x ( 2 . 3 , 4 . 1 , 6 ) m i n i m u m = m i n ( 2 . 3 , 4 . 1 , 6 ) a b s o l u t e = a b s ( - 4 2 ) p r i n t m a x i m u m 29 / 121
30. Functions Function: t y p e p r i n t t y p e ( 4 2 ) # < t y p e ' i n t ' > p r i n t t y p e ( 4 . 2 ) # < t y p e ' f l o a t ' > p r i n t t y p e ( ' s p a m ' ) # < t y p e ' s t r ' > # - - - d e f s p e a k ( m e s s a g e ) : r e t u r n m e s s a g e i f h a p p y ( ) : s p e a k ( " I ' m h a p p y ! " ) e l i f s a d ( ) : s p e a k ( " I ' m s a d . " ) e l s e : s p e a k ( " I d o n ' t k n o w w h a t I ' m f e e l i n g . " ) # - - - d e f s h u t _ d o w n ( s ) : i f s = = " y e s " : r e t u r n " S h u t t i n g d o w n " e l i f s = = " n o " : r e t u r n " S h u t d o w n a b o r t e d " e l s e : r e t u r n " S o r r y " 30 / 121
31. Functions d e f i s _ n u m e r i c ( n u m ) : r e t u r n t y p e ( n u m ) = = i n t o r t y p e ( n u m ) = = f l o a t : # - - - d e f d i s t a n c e _ f r o m _ z e r o ( a ) : i f t y p e ( a ) = = i n t o r t y p e ( a ) = = f l o a t : r e t u r n a b s ( a ) e l s e : r e t u r n " N o p e " 31 / 121
32. Functions Taking a Vacation d e f h o t e l _ c o s t ( n i g h t s ) : r e t u r n 1 4 0 * n i g h t s d e f p l a n e _ r i d e _ c o s t ( c i t y ) : i f c i t y = = " C h a r l o t t e " : r e t u r n 1 8 3 e l i f c i t y = = " T a m p a " : r e t u r n 2 2 0 e l i f c i t y = = " P i t t s b u r g h " : r e t u r n 2 2 2 e l i f c i t y = = " L o s A n g e l e s " : r e t u r n 4 7 5 d e f r e n t a l _ c a r _ c o s t ( d a y s ) : c o s t p e r d a y = 4 0 i f d a y s > = 7 : t o t a l = d a y s * c o s t p e r d a y - 5 0 e l i f d a y s > = 3 : t o t a l = d a y s * c o s t p e r d a y - 2 0 e l s e : t o t a l = d a y s * c o s t p e r d a y r e t u r n t o t a l d e f t r i p _ c o s t ( c i t y , d a y s , s p e n d i n g _ m o n e y ) : r e t u r n r e n t a l _ c a r _ c o s t ( d a y s ) + h o t e l _ c o s t ( d a y s ) + p l a n e _ r i d e _ c o s t ( c i t y ) + s p e n d i n g _ m o n e y p r i n t t r i p _ c o s t ( " L o s A n g e l e s " , 5 , 6 0 0 ) 32 / 121
33. Agenda 1. Python Syntax 2. Strings and Console Output 3. Conditionals and Control Flow 4. Functions 5. Lists and Dictionaries 6. Lists and Functions 7. Loops 8. Advanced Topics in Python 9. Introduction to Classes 10. File Input and Output 33 / 121
34. Lists and Dictionaries List : Array Dictionary : Asc. Array (notation {} -> object in JS) List # l i s t _ n a m e = [ i t e m _ 1 , i t e m _ 2 ] , e m p t y [ ] z o o _ a n i m a l s = [ " p a n g o l i n " , " c a s s o w a r y " , " s l o t h " , " g a j a h " ] ; i f l e n ( z o o _ a n i m a l s ) > 3 : p r i n t " T h e f i r s t a n i m a l a t t h e z o o i s t h e " + z o o _ a n i m a l s [ 0 ] p r i n t " T h e s e c o n d a n i m a l a t t h e z o o i s t h e " + z o o _ a n i m a l s [ 1 ] p r i n t " T h e t h i r d a n i m a l a t t h e z o o i s t h e " + z o o _ a n i m a l s [ 2 ] p r i n t " T h e f o u r t h a n i m a l a t t h e z o o i s t h e " + z o o _ a n i m a l s [ 3 ] 34 / 121
35. Lists and Dictionaries List Methods: a p p e n d , l e n s u i t c a s e = [ ] s u i t c a s e . a p p e n d ( " s u n g l a s s e s " ) # Y o u r c o d e h e r e ! s u i t c a s e . a p p e n d ( ' a ' ) s u i t c a s e . a p p e n d ( ' b ' ) s u i t c a s e . a p p e n d ( ' c ' ) l i s t _ l e n g t h = l e n ( s u i t c a s e ) # S e t t h i s t o t h e l e n g t h o f s u i t c a s e p r i n t " T h e r e a r e % d i t e m s i n t h e s u i t c a s e . " % ( l i s t _ l e n g t h ) p r i n t s u i t c a s e " " " T h e r e a r e 4 i t e m s i n t h e s u i t c a s e . [ ' s u n g l a s s e s ' , ' a ' , ' b ' , ' c ' ] " " " 35 / 121
36. Lists and Dictionaries List Slicing: [ i n d e x _ i n c l u s i v e : i n d e x _ e x c l u s i v e ] s u i t c a s e = [ " s u n g l a s s e s " , " h a t " , " p a s s p o r t " , " l a p t o p " , " s u i t " , " s h o e s " ] f i r s t = s u i t c a s e [ 0 : 2 ] # T h e f i r s t a n d s e c o n d i t e m s ( i n d e x z e r o a n d o n e ) m i d d l e = s u i t c a s e [ 2 : 4 ] # T h i r d a n d f o u r t h i t e m s ( i n d e x t w o a n d t h r e e ) l a s t = s u i t c a s e [ 4 : 6 ] # T h e l a s t t w o i t e m s ( i n d e x f o u r a n d f i v e ) # < 6 b u k a n < = 6 # W e s t a r t a t t h e i n d e x b e f o r e t h e c o l o n a n d c o n t i n u e u p t o b u t n o t i n c l u d i n g t h e i n d e x a f t e r t h e c o l o n . # - - - a n i m a l s = " c a t d o g f r o g " c a t = a n i m a l s [ : 3 ] # T h e f i r s t t h r e e c h a r a c t e r s o f a n i m a l s d o g = a n i m a l s [ 3 : 6 ] # T h e f o u r t h t h r o u g h s i x t h c h a r a c t e r s f r o g = a n i m a l s [ 6 : ] # F r o m t h e s e v e n t h c h a r a c t e r t o t h e e n d # t a n p a s t a r t / e n d 36 / 121
37. Lists and Dictionaries List Methods: i n d e x , i n s e r t a n i m a l s = [ " a a r d v a r k " , " b a d g e r " , " d u c k " , " e m u " , " f e n n e c f o x " ] d u c k _ i n d e x = a n i m a l s . i n d e x ( " d u c k " ) # U s e i n d e x ( ) t o f i n d " d u c k " # Y o u r c o d e h e r e ! a n i m a l s . i n s e r t ( d u c k _ i n d e x , " c o b r a " ) p r i n t a n i m a l s # O b s e r v e w h a t p r i n t s a f t e r t h e i n s e r t o p e r a t i o n # [ ' a a r d v a r k ' , ' b a d g e r ' , ' c o b r a ' , ' d u c k ' , ' e m u ' , ' f e n n e c f o x ' ] 37 / 121
38. Lists and Dictionaries List f o r e l e m e n t i n t h e _ l i s t . s o r t ( ) # 1 m y _ l i s t = [ 1 , 9 , 3 , 8 , 5 , 7 ] f o r n u m b e r i n m y _ l i s t : p r i n t 2 * n u m b e r # 2 # . s o r t s t a r t _ l i s t = [ 5 , 3 , 1 , 2 , 4 ] s q u a r e _ l i s t = [ ] f o r n u m i n s t a r t _ l i s t : s q u a r e _ l i s t . a p p e n d ( n u m * * 2 ) s q u a r e _ l i s t . s o r t ( ) p r i n t s q u a r e _ l i s t 38 / 121
39. Lists and Dictionaries Dict Key : Value Pair # d i c t i o n a r y k e y v a l u e n o t a s i o b j e c t { } r e s i d e n t s = { ' P u f f i n ' : 1 0 4 , ' S l o t h ' : 1 0 5 , ' B u r m e s e P y t h o n ' : 1 0 6 } p r i n t r e s i d e n t s [ ' P u f f i n ' ] # P r i n t s P u f f i n ' s r o o m n u m b e r # Y o u r c o d e h e r e ! p r i n t r e s i d e n t s [ ' S l o t h ' ] p r i n t r e s i d e n t s [ ' B u r m e s e P y t h o n ' ] 39 / 121
40. Lists and Dictionaries Dict # - - - m e n u = { } # E m p t y d i c t i o n a r y m e n u [ ' C h i c k e n A l f r e d o ' ] = 1 4 . 5 0 # A d d i n g n e w k e y - v a l u e p a i r p r i n t m e n u [ ' C h i c k e n A l f r e d o ' ] # a p p e n d m e n u [ ' k a r e d o k ' ] = 2 . 2 m e n u [ ' l o t e k ' ] = 2 . 3 m e n u [ ' r u j a k ' ] = 3 . 3 p r i n t " T h e r e a r e " + s t r ( l e n ( m e n u ) ) + " i t e m s o n t h e m e n u . " p r i n t m e n u " " " 1 4 . 5 T h e r e a r e 4 i t e m s o n t h e m e n u . { ' l o t e k ' : 2 . 3 , ' C h i c k e n A l f r e d o ' : 1 4 . 5 , ' k a r e d o k ' : 2 . 2 , ' r u j a k ' : 3 . 3 } " " " 40 / 121
41. Lists and Dictionaries Dict A dictionary (or list) declaration may break across multiple lines d e l # k e y - a n i m a l _ n a m e : v a l u e - l o c a t i o n z o o _ a n i m a l s = { ' U n i c o r n ' : ' C o t t o n C a n d y H o u s e ' , ' S l o t h ' : ' R a i n f o r e s t E x h i b i t ' , ' B e n g a l T i g e r ' : ' J u n g l e H o u s e ' , ' A t l a n t i c P u f f i n ' : ' A r c t i c E x h i b i t ' , ' R o c k h o p p e r P e n g u i n ' : ' A r c t i c E x h i b i t ' } # R e m o v i n g t h e ' U n i c o r n ' e n t r y . ( U n i c o r n s a r e i n c r e d i b l y e x p e n s i v e . ) d e l z o o _ a n i m a l s [ ' U n i c o r n ' ] d e l z o o _ a n i m a l s [ ' S l o t h ' ] d e l z o o _ a n i m a l s [ ' B e n g a l T i g e r ' ] z o o _ a n i m a l s [ ' R o c k h o p p e r P e n g u i n ' ] = ' A r c t i c E x h i b i t M o d ' p r i n t z o o _ a n i m a l s 41 / 121
42. Lists and Dictionaries List & Dict r e m o v e Complex Dict # r e m o v e b a c k p a c k = [ ' x y l o p h o n e ' , ' d a g g e r ' , ' t e n t ' , ' b r e a d l o a f ' ] b a c k p a c k . r e m o v e ( " d a g g e r " ) # - - - i n v e n t o r y = { ' g o l d ' : 5 0 0 , ' p o u c h ' : [ ' f l i n t ' , ' t w i n e ' , ' g e m s t o n e ' ] , # A s s i g n e d a n e w l i s t t o ' p o u c h ' k e y ' b a c k p a c k ' : [ ' x y l o p h o n e ' , ' d a g g e r ' , ' b e d r o l l ' , ' b r e a d l o a f ' ] } # A d d i n g a k e y ' b u r l a p b a g ' a n d a s s i g n i n g a l i s t t o i t i n v e n t o r y [ ' b u r l a p b a g ' ] = [ ' a p p l e ' , ' s m a l l r u b y ' , ' t h r e e - t o e d s l o t h ' ] # S o r t i n g t h e l i s t f o u n d u n d e r t h e k e y ' p o u c h ' i n v e n t o r y [ ' p o u c h ' ] . s o r t ( ) i n v e n t o r y [ ' p o c k e t ' ] = [ ' s e a s h e l l ' , ' s t r a n g e b e r r y ' , ' l i n t ' ] i n v e n t o r y [ ' b a c k p a c k ' ] . s o r t ( ) i n v e n t o r y [ ' b a c k p a c k ' ] . r e m o v e ( ' d a g g e r ' ) i n v e n t o r y [ ' g o l d ' ] + = 5 0 42 / 121
43. Lists and Dictionaries A Day at the Supermarket n a m e s = [ " A d a m " , " A l e x " , " M a r i a h " , " M a r t i n e " , " C o l u m b u s " ] f o r i t e m i n n a m e s : p r i n t i t e m # - - - # i n d e n t f i r s t e l e m e n t d a l a m d i c t d a l a m { } , s p t d i b h s l a i n w e b s t e r = { " A a r d v a r k " : " A s t a r o f a p o p u l a r c h i l d r e n ' s c a r t o o n s h o w . " , " B a a " : " T h e s o u n d a g o a t m a k e s . " , " C a r p e t " : " G o e s o n t h e f l o o r . " , " D a b " : " A s m a l l a m o u n t . " } f o r k e y i n w e b s t e r : p r i n t w e b s t e r [ k e y ] Note that dictionaries are unordered, meaning that any time you loop through a dictionary, you will go through every key, but you are not guaranteed to get them in any particular order. 43 / 121
44. Lists and Dictionaries A Day at the Supermarket a = [ 0 , 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 1 0 , 1 1 , 1 2 , 1 3 ] f o r n u m b e r i n a : i f n u m b e r % 2 = = 0 : p r i n t n u m b e r # - - - d e f c o u n t _ s m a l l ( n u m b e r s ) : t o t a l = 0 f o r n i n n u m b e r s : i f n < 1 0 : t o t a l = t o t a l + 1 r e t u r n t o t a l l o s t = [ 4 , 8 , 1 5 , 1 6 , 2 3 , 4 2 ] s m a l l = c o u n t _ s m a l l ( l o s t ) p r i n t s m a l l # - - - d e f f i z z _ c o u n t ( x ) : c o u n t = 0 f o r i t e m i n x : i f i t e m = = ' f i z z ' : c o u n t + = 1 r e t u r n c o u n t f i z z _ c o u n t ( [ " f i z z " , " c a t " , " f i z z " ] ) 44 / 121
45. Lists and Dictionaries A Day at the Supermarket As we've mentioned, strings are like lists with characters as elements. You can loop through strings the same way you loop through lists! f o r l e t t e r i n " C o d e c a d e m y " : p r i n t l e t t e r # E m p t y l i n e s t o m a k e t h e o u t p u t p r e t t y p r i n t p r i n t w o r d = " P r o g r a m m i n g i s f u n ! " f o r l e t t e r i n w o r d : # O n l y p r i n t o u t t h e l e t t e r i i f l e t t e r = = " i " : p r i n t l e t t e r 45 / 121
46. Lists and Dictionaries A Day at the Supermarket p r i c e s = { " b a n a n a " : 4 , " a p p l e " : 2 , " o r a n g e " : 1 . 5 , " p e a r " : 3 } s t o c k = { " b a n a n a " : 6 , " a p p l e " : 0 , " o r a n g e " : 3 2 , " p e a r " : 1 5 } f o r k e y i n s t o c k : p r i n t k e y p r i n t " p r i c e : % s " % p r i c e s [ k e y ] p r i n t " s t o c k : % s " % s t o c k [ k e y ] 46 / 121
47. Lists and Dictionaries A Day at the Supermarket # t a k e 2 p r i c e s = { " b a n a n a " : 4 , " a p p l e " : 2 , " o r a n g e " : 1 . 5 , " p e a r " : 3 , } s t o c k = { " b a n a n a " : 6 , " a p p l e " : 0 , " o r a n g e " : 3 2 , " p e a r " : 1 5 , } f o r k e y i n p r i c e s : p r i n t k e y p r i n t " p r i c e : % s " % p r i c e s [ k e y ] p r i n t " s t o c k : % s " % s t o c k [ k e y ] t o t a l = 0 f o r k e y i n p r i c e s : p r i n t p r i c e s [ k e y ] * s t o c k [ k e y ] t o t a l + = p r i c e s [ k e y ] * s t o c k [ k e y ] p r i n t t o t a l 47 / 121
48. Lists and Dictionaries A Day at the Supermarket # t a k e 3 s h o p p i n g _ l i s t = [ " b a n a n a " , " o r a n g e " , " a p p l e " ] s t o c k = { " b a n a n a " : 6 , " a p p l e " : 0 , " o r a n g e " : 3 2 , " p e a r " : 1 5 } p r i c e s = { " b a n a n a " : 4 , " a p p l e " : 2 , " o r a n g e " : 1 . 5 , " p e a r " : 3 } d e f c o m p u t e _ b i l l ( f o o d ) : t o t a l = 0 f o r i t e m i n f o o d : i f s t o c k [ i t e m ] > 0 : t o t a l + = p r i c e s [ i t e m ] s t o c k [ i t e m ] - = 1 r e t u r n t o t a l 48 / 121
49. Student Becomes the Teacher List of Dicts l l o y d = { " n a m e " : " L l o y d " , " h o m e w o r k " : [ 9 0 . 0 , 9 7 . 0 , 7 5 . 0 , 9 2 . 0 ] , " q u i z z e s " : [ 8 8 . 0 , 4 0 . 0 , 9 4 . 0 ] , " t e s t s " : [ 7 5 . 0 , 9 0 . 0 ] } a l i c e = { " n a m e " : " A l i c e " , " h o m e w o r k " : [ 1 0 0 . 0 , 9 2 . 0 , 9 8 . 0 , 1 0 0 . 0 ] , " q u i z z e s " : [ 8 2 . 0 , 8 3 . 0 , 9 1 . 0 ] , " t e s t s " : [ 8 9 . 0 , 9 7 . 0 ] } t y l e r = { " n a m e " : " T y l e r " , " h o m e w o r k " : [ 0 . 0 , 8 7 . 0 , 7 5 . 0 , 2 2 . 0 ] , " q u i z z e s " : [ 0 . 0 , 7 5 . 0 , 7 8 . 0 ] , " t e s t s " : [ 1 0 0 . 0 , 1 0 0 . 0 ] } s t u d e n t s = [ l l o y d , a l i c e , t y l e r ] f o r s t u d e n t i n s t u d e n t s : p r i n t s t u d e n t [ ' n a m e ' ] p r i n t s t u d e n t [ ' h o m e w o r k ' ] p r i n t s t u d e n t [ ' q u i z z e s ' ] p r i n t s t u d e n t [ ' t e s t s ' ] 49 / 121
50. Student Becomes the Teacher Arithmetics Notes 5 / 2 # 2 5 . 0 / 2 # 2 . 5 f l o a t ( 5 ) / 2 # 2 . 5 b i a r j a d i f l o a t k a r e n a i n t / i n t 50 / 121
51. Student Becomes the Teacher l l o y d = { " n a m e " : " L l o y d " , " h o m e w o r k " : [ 9 0 . 0 , 9 7 . 0 , 7 5 . 0 , 9 2 . 0 ] , " q u i z z e s " : [ 8 8 . 0 , 4 0 . 0 , 9 4 . 0 ] , " t e s t s " : [ 7 5 . 0 , 9 0 . 0 ] } a l i c e = { " n a m e " : " A l i c e " , " h o m e w o r k " : [ 1 0 0 . 0 , 9 2 . 0 , 9 8 . 0 , 1 0 0 . 0 ] , " q u i z z e s " : [ 8 2 . 0 , 8 3 . 0 , 9 1 . 0 ] , " t e s t s " : [ 8 9 . 0 , 9 7 . 0 ] } t y l e r = { " n a m e " : " T y l e r " , " h o m e w o r k " : [ 0 . 0 , 8 7 . 0 , 7 5 . 0 , 2 2 . 0 ] , " q u i z z e s " : [ 0 . 0 , 7 5 . 0 , 7 8 . 0 ] , " t e s t s " : [ 1 0 0 . 0 , 1 0 0 . 0 ] } # - - - d e f a v e r a g e ( n u m b e r s ) : t o t a l = s u m ( n u m b e r s ) t o t a l = f l o a t ( t o t a l ) r e t u r n t o t a l / l e n ( n u m b e r s ) d e f g e t _ a v e r a g e ( s t u d e n t ) : h o m e w o r k = a v e r a g e ( s t u d e n t [ ' h o m e w o r k ' ] ) q u i z z e s = a v e r a g e ( s t u d e n t [ ' q u i z z e s ' ] ) t e s t s = a v e r a g e ( s t u d e n t [ ' t e s t s ' ] ) r e t u r n 0 . 1 * h o m e w o r k + 0 . 3 * q u i z z e s + 0 . 6 * t e s t s d e f g e t _ l e t t e r _ g r a d e ( s c o r e ) : i f s c o r e > = 9 0 : r e t u r n " A " e l i f s c o r e > = 8 0 : r e t u r n " B " e l i f s c o r e > = 7 0 : r e t u r n " C " e l i f s c o r e > = 6 0 : r e t u r n " D " e l s e : r e t u r n " F " d e f g e t _ c l a s s _ a v e r a g e ( s t u d e n t s ) : r e s u l t s = [ ] f o r s t u d e n t i n s t u d e n t s : r e s u l t s . a p p e n d ( g e t _ a v e r a g e ( s t u d e n t ) ) r e t u r n a v e r a g e ( r e s u l t s ) 51 / 121
52. Student Becomes the Teacher a v e r a g e ( A - L i s t ) returns f l o a t g e t _ a v e r a g e ( A - D i c t ) returns f l o a t --> better g e t _ n u m e r i c _ g r a d e ( ) g e t _ l e t t e r _ g r a d e ( n u m ) returns s t r i n g g e t _ c l a s s _ a v e r a g e ( L i s t - o f - D i c t s ) returns f l o a t # - - - s t u d e n t s = [ l l o y d , a l i c e , t y l e r ] p r i n t g e t _ c l a s s _ a v e r a g e ( s t u d e n t s ) p r i n t g e t _ l e t t e r _ g r a d e ( g e t _ c l a s s _ a v e r a g e ( s t u d e n t s ) ) # - - - # c l a s s a v e r a g e = g e t _ c l a s s _ a v e r a g e ( [ l l o y d , a l i c e , t y l e r ] ) # p r i n t g e t _ l e t t e r _ g r a d e ( g e t _ a v e r a g e ( l l o y d ) ) # - - - 52 / 121
53. Agenda 1. Python Syntax 2. Strings and Console Output 3. Conditionals and Control Flow 4. Functions 5. Lists and Dictionaries 6. Lists and Functions 7. Loops 8. Advanced Topics in Python 9. Introduction to Classes 10. File Input and Output 53 / 121
54. Lists and Functions Access to List Method: . a p p e n d ( ) , . p o p ( ) , . r e m o v e ( ) Function: d e l n = [ 1 , 3 , 5 ] # D o y o u r m u l t i p l i c a t i o n h e r e n [ 1 ] * = 5 n . a p p e n d ( 4 ) p r i n t n # [ 1 , 1 5 , 5 , 4 ] n = [ 1 , 3 , 5 ] # R e m o v e t h e f i r s t i t e m i n t h e l i s t h e r e n . p o p ( 0 ) # a t a u d e l ( n [ 0 ] ) # n . r e m o v e ( 1 ) v a l u e 1 , b u k a n i n d e x # p o p n g e - r e t u r n v a l u e , d e l v o i d p r i n t n 54 / 121
55. Lists and Functions # 1 n = " H e l l o " d e f s t r i n g _ f u n c t i o n ( s ) : r e t u r n s + ' w o r l d ' p r i n t s t r i n g _ f u n c t i o n ( n ) # 2 d e f l i s t _ f u n c t i o n ( x ) : x [ 1 ] + = 3 r e t u r n x n = [ 3 , 5 , 7 ] p r i n t l i s t _ f u n c t i o n ( n ) # 3 n = [ 3 , 5 , 7 ] d e f l i s t _ e x t e n d e r ( l s t ) : l s t . a p p e n d ( 9 ) ; r e t u r n l s t p r i n t l i s t _ e x t e n d e r ( n ) 55 / 121
56. Lists and Functions # 1 r a n g e n = [ 3 , 5 , 7 ] d e f p r i n t _ l i s t ( x ) : f o r i i n r a n g e ( 0 , l e n ( x ) ) : p r i n t x [ i ] p r i n t _ l i s t ( n ) # e a c h l i n e : 3 5 7 # 2 n = [ 3 , 5 , 7 ] d e f d o u b l e _ l i s t ( x ) : f o r i i n r a n g e ( 0 , l e n ( x ) ) : x [ i ] = x [ i ] * 2 r e t u r n x p r i n t d o u b l e _ l i s t ( n ) # [ 6 , 1 0 , 1 4 ] 56 / 121
57. Lists and Functions # 3 r a n g e ( 6 ) # = > [ 0 , 1 , 2 , 3 , 4 , 5 ] r a n g e ( 1 , 6 ) # = > [ 1 , 2 , 3 , 4 , 5 ] r a n g e ( 1 , 6 , 3 ) # = > [ 1 , 4 ] # r a n g e ( s t o p ) # r a n g e ( s t a r t , s t o p ) # r a n g e ( s t a r t , s t o p , s t e p ) d e f m y _ f u n c t i o n ( x ) : f o r i i n r a n g e ( 0 , l e n ( x ) ) : x [ i ] = x [ i ] * 2 r e t u r n x p r i n t m y _ f u n c t i o n ( r a n g e ( 3 ) ) # [ 0 , 1 , 2 ] # [ 0 , 2 , 4 ] 57 / 121
58. Lists and Functions # 1 n = [ 3 , 5 , 7 ] d e f t o t a l ( n u m b e r s ) : r e s u l t = 0 f o r n u m i n n u m b e r s : # f o r i i n r a n g e ( l e n ( n u m b e r s ) ) : r e s u l t + = n u m # r e s u l t + = n u m b e r s [ i ] r e t u r n r e s u l t # 2 n = [ " M i c h a e l " , " L i e b e r m a n " ] d e f j o i n _ s t r i n g s ( w o r d s ) : r e s u l t = " " f o r i t e m i n w o r d s : r e s u l t + = i t e m r e t u r n r e s u l t p r i n t j o i n _ s t r i n g s ( n ) 58 / 121
59. Lists and Functions # 3 o p e r a t o r + a g a k b e d a d i p y t h o n b u a t l i s t m = [ 1 , 2 , 3 ] n = [ 4 , 5 , 6 ] d e f j o i n _ l i s t s ( x , y ) : r e t u r n x + y p r i n t j o i n _ l i s t s ( m , n ) # [ 1 , 2 , 3 , 4 , 5 , 6 ] # 4 L i s t o f L i s t s n = [ [ 1 , 2 , 3 ] , [ 4 , 5 , 6 , 7 , 8 , 9 ] ] d e f f l a t t e n ( l i s t s ) : r e s u l t s = [ ] f o r n u m b e r s i n l i s t s : f o r n u m i n n u m b e r s : r e s u l t s . a p p e n d ( n u m ) r e t u r n r e s u l t s p r i n t f l a t t e n ( n ) # [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 ] 59 / 121
60. Lists and Functions Battleship! In this project you will build a simplified, one-player version of the classic board game Battleship! In this version of the game, there will be a single ship hidden in a random location on a 5x5 grid. The player will have 10 guesses to try to sink the ship. # t a m b a h e l e m e n b e r u l a n g p d l i s t b o a r d = [ ] f o r i i n r a n g e ( 5 ) : b o a r d . a p p e n d ( [ " O " ] * 5 ) # [ " O " , " O " , " O " , " O " , " O " ] p r i n t b o a r d # [ [ ] , . . , [ ] ] # p r i n t 1 r o w e l e m e n , 1 b a r i s b o a r d = [ ] f o r i i n r a n g e ( 5 ) : b o a r d . a p p e n d ( [ " O " ] * 5 ) # [ " O " , " O " , " O " , " O " , " O " ] d e f p r i n t _ b o a r d ( b o a r d ) : f o r r o w i n b o a r d : p r i n t r o w p r i n t _ b o a r d ( b o a r d ) 60 / 121
61. Lists and Functions Battleship! (1) # . j o i n m e t h o d u s e s t h e s t r i n g t o c o m b i n e t h e i t e m s i n t h e l i s t . f r o m r a n d o m i m p o r t r a n d i n t b o a r d = [ ] f o r x i n r a n g e ( 5 ) : b o a r d . a p p e n d ( [ " O " ] * 5 ) d e f p r i n t _ b o a r d ( b o a r d ) : f o r r o w i n b o a r d : p r i n t " " . j o i n ( r o w ) p r i n t " L e t ' s p l a y B a t t l e s h i p ! " p r i n t _ b o a r d ( b o a r d ) # - - - d e f r a n d o m _ r o w ( b o a r d ) : r e t u r n r a n d i n t ( 0 , l e n ( b o a r d ) - 1 ) d e f r a n d o m _ c o l ( b o a r d ) : r e t u r n r a n d i n t ( 0 , l e n ( b o a r d [ 0 ] ) - 1 ) s h i p _ r o w = r a n d o m _ r o w ( b o a r d ) s h i p _ c o l = r a n d o m _ c o l ( b o a r d ) # p r i n t s h i p _ r o w # p r i n t s h i p _ c o l 61 / 121
62. Lists and Functions Battleship! (2) # M u l t i l i n e i f c o n d i t i o n , g u e s s _ r o w n o t i n r a n g e ( 5 ) f o r t u r n i n r a n g e ( 4 ) : p r i n t " T u r n " , t u r n + 1 g u e s s _ r o w = i n t ( r a w _ i n p u t ( " G u e s s R o w : " ) ) g u e s s _ c o l = i n t ( r a w _ i n p u t ( " G u e s s C o l : " ) ) i f g u e s s _ r o w = = s h i p _ r o w a n d g u e s s _ c o l = = s h i p _ c o l : p r i n t " C o n g r a t u l a t i o n s ! Y o u s a n k m y b a t t l e s h i p ! " b r e a k e l s e : i f ( g u e s s _ r o w < 0 o r g u e s s _ r o w > 4 ) o r \ ( g u e s s _ c o l < 0 o r g u e s s _ c o l > 4 ) : p r i n t " O o p s , t h a t ' s n o t e v e n i n t h e o c e a n . " e l i f ( b o a r d [ g u e s s _ r o w ] [ g u e s s _ c o l ] = = " X " ) : p r i n t " Y o u g u e s s e d t h a t o n e a l r e a d y . " e l s e : p r i n t " Y o u m i s s e d m y b a t t l e s h i p ! " b o a r d [ g u e s s _ r o w ] [ g u e s s _ c o l ] = " X " p r i n t _ b o a r d ( b o a r d ) i f t u r n = = 3 : p r i n t " G a m e O v e r " 62 / 121
63. Agenda 1. Python Syntax 2. Strings and Console Output 3. Conditionals and Control Flow 4. Functions 5. Lists and Dictionaries 6. Lists and Functions 7. Loops 8. Advanced Topics in Python 9. Introduction to Classes 10. File Input and Output 63 / 121
64. Loops w h i l e # 1 c o u n t = 0 i f c o u n t < 5 : p r i n t " H e l l o , I a m a n i f s t a t e m e n t a n d c o u n t i s " , c o u n t w h i l e c o u n t < = 9 : p r i n t " H e l l o , I a m a w h i l e a n d c o u n t i s " , c o u n t c o u n t + = 1 # - - - # 2 l o o p _ c o n d i t i o n = T r u e w h i l e l o o p _ c o n d i t i o n : p r i n t " I a m a l o o p " l o o p _ c o n d i t i o n = F a l s e # - - - # 3 n u m = 1 w h i l e n u m < = 1 0 : # F i l l i n t h e c o n d i t i o n p r i n t n u m * * 2 n u m + = 1 64 / 121
65. Loops w h i l e , b r e a k # - - - # 4 c h o i c e = r a w _ i n p u t ( ' E n j o y i n g t h e c o u r s e ? ( y / n ) ' ) w h i l e c h o i c e ! = ' y ' a n d c h o i c e ! = ' n ' : c h o i c e = r a w _ i n p u t ( " S o r r y , I d i d n ' t c a t c h t h a t . E n t e r a g a i n : " ) # - - - # 5 b r e a k c o u n t = 0 w h i l e T r u e : p r i n t c o u n t c o u n t + = 1 i f c o u n t > = 1 0 : b r e a k # - - - 65 / 121
66. Loops w h i l e , e l s e # 6 w h i l e e l s e i m p o r t r a n d o m p r i n t " L u c k y N u m b e r s ! 3 n u m b e r s w i l l b e g e n e r a t e d . " p r i n t " I f o n e o f t h e m i s a ' 5 ' , y o u l o s e ! " c o u n t = 0 w h i l e c o u n t < 3 : n u m = r a n d o m . r a n d i n t ( 1 , 6 ) p r i n t n u m i f n u m = = 5 : p r i n t " S o r r y , y o u l o s e ! " b r e a k c o u n t + = 1 e l s e : p r i n t " Y o u w i n ! " # e l s e d i e k s e k u s i s e t e l a h k o n d i s i f a l s e ; t d k p e r n a h d i e k s e k u s i s e t e l a h b r e a k # - - - 66 / 121
67. Loops w h i l e , e l s e # 7 f r o m r a n d o m i m p o r t r a n d i n t # G e n e r a t e s a n u m b e r f r o m 1 t h r o u g h 1 0 i n c l u s i v e r a n d o m _ n u m b e r = r a n d i n t ( 1 , 1 0 ) g u e s s e s _ l e f t = 3 w h i l e g u e s s e s _ l e f t > 0 : g u e s s = i n t ( r a w _ i n p u t ( " Y o u r g u e s s : " ) ) i f g u e s s = = r a n d o m _ n u m b e r : p r i n t ' Y o u w i n ! ' b r e a k g u e s s e s _ l e f t - = 1 e l s e : p r i n t ' Y o u l o s e . ' 67 / 121
68. Loops f o r i n # 1 h o b b i e s = [ ] # A d d y o u r c o d e b e l o w ! f o r i i n r a n g e ( 3 ) : h o b b y = s t r ( r a w _ i n p u t ( " Y o u r h o b b y : " ) ) h o b b i e s . a p p e n d ( h o b b y ) ; # - - - # 2 t h i n g = " s p a m ! " f o r c i n t h i n g : p r i n t c w o r d = " e g g s ! " f o r c i n w o r d : p r i n t c 68 / 121
69. Loops f o r i n Looping over a Dictionary # 3 p h r a s e = " A b i r d i n t h e h a n d . . . " f o r c h a r i n p h r a s e : i f c h a r = = " A " o r c h a r = = " a " : p r i n t " X " , e l s e : p r i n t c h a r , p r i n t # T h e , c h a r a c t e r a f t e r o u r p r i n t s t a t e m e n t m e a n s t h a t # o u r n e x t p r i n t s t a t e m e n t k e e p s p r i n t i n g o n t h e s a m e l i n e . # p l u s 1 s p a c e # - - - # 4 L o o p i n g o v e r a d i c t i o n a r y d = { ' a ' : ' a p p l e ' , ' b ' : ' b e r r y ' , ' c ' : ' c h e r r y ' } f o r k e y i n d : p r i n t k e y + " " + d [ k e y ] 69 / 121
70. Loops f o r i n d e x , i t e m i n e n u m e r a t e ( l i s t ) f o r a , b i n z i p ( l i s t _ a , l i s t _ b ) # 5 c h o i c e s = [ ' p i z z a ' , ' p a s t a ' , ' s a l a d ' , ' n a c h o s ' ] p r i n t ' Y o u r c h o i c e s a r e : ' f o r i n d e x , i t e m i n e n u m e r a t e ( c h o i c e s ) : p r i n t i n d e x + 1 , i t e m # - - - # 6 l i s t _ a = [ 3 , 9 , 1 7 , 1 5 , 1 9 ] l i s t _ b = [ 2 , 4 , 8 , 1 0 , 3 0 , 4 0 , 5 0 , 6 0 , 7 0 , 8 0 , 9 0 ] f o r a , b i n z i p ( l i s t _ a , l i s t _ b ) : # A d d y o u r c o d e h e r e ! i f a > b : p r i n t a e l s e : p r i n t b # z i p w i l l c r e a t e p a i r s o f e l e m e n t s w h e n p a s s e d t w o l i s t s , # a n d w i l l s t o p a t t h e e n d o f t h e s h o r t e r l i s t . # z i p c a n h a n d l e t h r e e o r m o r e l i s t s a s w e l l ! 70 / 121
71. Loops f o r , e l s e # 7 f r u i t s = [ ' b a n a n a ' , ' a p p l e ' , ' o r a n g e ' , ' t o m a t o ' , ' p e a r ' , ' g r a p e ' ] p r i n t ' Y o u h a v e . . . ' f o r f i n f r u i t s : i f f = = ' t o m a t o ' : p r i n t ' A t o m a t o i s n o t a f r u i t ! ' # ( I t a c t u a l l y i s . ) b r e a k p r i n t ' A ' , f e l s e : p r i n t ' A f i n e s e l e c t i o n o f f r u i t s ! ' # s p t e l s e w h i l e , k l b r e a k t i d a k d i r u n , k l e x i t n o r m a l y e s # - - - 71 / 121
72. Loops f o r , e l s e # 8 f r u i t s = [ ' b a n a n a ' , ' a p p l e ' , ' o r a n g e ' , ' t o m a t o ' , ' p e a r ' , ' g r a p e ' ] p r i n t ' Y o u h a v e . . . ' f o r f i n f r u i t s : i f f = = ' t o m a t o 1 ' : # k l m a t c h , e x e c u t e d ; e l s e n e v e r p r i n t ' A t o m a t o i s n o t a f r u i t ! ' b r e a k p r i n t ' A ' , f e l s e : p r i n t ' A f i n e s e l e c t i o n o f f r u i t s ! ' # - - - # 9 t h e l i s t = [ ' a ' , ' b ' , ' c ' ] f o r i i n t h e l i s t : p r i n t i e l s e : p r i n t ' c o m p l e t e d ! ' 72 / 121
73. Loops Practice Makes Perfect # 1 d e f i s _ e v e n ( x ) : i f x % 2 = = 0 : r e t u r n T r u e e l s e : r e t u r n F a l s e # - - - # 2 d e f i s _ i n t ( x ) : d e l t a = x - i n t ( x ) i f d e l t a = = 0 . 0 : r e t u r n T r u e e l s e : r e t u r n F a l s e p r i n t i s _ i n t ( 7 . 0 ) p r i n t i s _ i n t ( 7 . 9 ) p r i n t i s _ i n t ( - 1 . 2 ) 73 / 121
74. Loops Practice Makes Perfect # - - - # 3 c a s t k e s t r , c a s t k e i n t d e f d i g i t _ s u m ( n ) : d s u m = 0 n _ s t r = s t r ( n ) f o r c i n n _ s t r : d s u m + = i n t ( c ) r e t u r n d s u m p r i n t d i g i t _ s u m ( 1 2 3 4 ) # - - - # 4 r e k u r s i f d e f f a c t o r i a l ( x ) : i f x = = 1 : r e t u r n 1 e l s e : r e t u r n x * f a c t o r i a l ( x - 1 ) p r i n t f a c t o r i a l ( 4 ) 74 / 121
75. Loops Practice Makes Perfect # 5 d e f i s _ p r i m e ( x ) : i f x < 2 : r e t u r n F a l s e f o r n i n r a n g e ( x - 2 ) : i f x % ( n + 2 ) = = 0 : r e t u r n F a l s e r e t u r n T r u e p r i n t i s _ p r i m e ( 9 ) p r i n t i s _ p r i m e ( 1 1 ) # - - - # 6 d e f r e v e r s e ( t e x t ) : v a r l e n g t h = l e n ( t e x t ) t e x t r e v = " " f o r i i n r a n g e ( v a r l e n g t h ) : t e x t r e v + = t e x t [ v a r l e n g t h - 1 - i ] r e t u r n t e x t r e v p r i n t r e v e r s e ( ' a b c @ d e f ' ) # Y o u m a y n o t u s e r e v e r s e d o r [ : : - 1 ] t o h e l p y o u w i t h t h i s . # - - - 75 / 121
76. Loops Practice Makes Perfect # 7 d e f a n t i _ v o w e l ( t e x t ) : r e t t e x t = " " f o r c i n t e x t : c l o w e r = c . l o w e r ( ) i f c l o w e r ! = ' a ' a n d c l o w e r ! = ' e ' a n d c l o w e r ! = ' i ' a n d c l o w e r ! = ' o ' a n d \ c l o w e r ! = ' u ' : r e t t e x t + = c r e t u r n r e t t e x t p r i n t a n t i _ v o w e l ( " H e y Y o u ! " ) # - - - s c o r e = { " a " : 1 , " c " : 3 , " b " : 3 , " e " : 1 , " d " : 2 , " g " : 2 , " f " : 4 , " i " : 1 , " h " : 4 , " k " : 5 , " j " : 8 , " m " : 3 , " l " d e f s c r a b b l e _ s c o r e ( w o r d ) : w o r d l o w e r = w o r d . l o w e r ( ) r e t s c o r e = 0 f o r c i n w o r d l o w e r : f o r k e y i n s c o r e : i f k e y = = c : r e t s c o r e + = s c o r e [ k e y ] b r e a k r e t u r n r e t s c o r e p r i n t s c r a b b l e _ s c o r e ( " H e l i x " ) 76 / 121
77. Loops Practice Makes Perfect # 8 d e f c e n s o r ( t e x t , w o r d ) : t e x t l i s t = t e x t . s p l i t ( ) t e x t l i s t _ n e w = [ ] f o r i t e m i n t e x t l i s t : i f i t e m ! = w o r d : t e x t l i s t _ n e w . a p p e n d ( i t e m ) e l s e : t e x t l i s t _ n e w . a p p e n d ( " * " * l e n ( i t e m ) ) r e t u r n " " . j o i n ( t e x t l i s t _ n e w ) p r i n t c e n s o r ( " t h i s h a c k i s w a c k h a c k " , " h a c k " ) # - - - # 9 d e f c o u n t ( s e q u e n c e , i t e m ) : v a r c o u n t = 0 f o r i i n s e q u e n c e : i f i = = i t e m : v a r c o u n t + = 1 r e t u r n v a r c o u n t p r i n t c o u n t ( [ 1 , 2 , 1 , 1 ] , 1 ) 77 / 121
78. Loops Practice Makes Perfect # 1 0 d e f p u r i f y ( n u m b e r s ) : r e t n u m b e r s = [ ] f o r n u m i n n u m b e r s : i f n u m % 2 = = 0 : r e t n u m b e r s . a p p e n d ( n u m ) r e t u r n r e t n u m b e r s p r i n t p u r i f y ( [ 1 , 2 , 3 ] ) # - - - # 1 1 d e f p r o d u c t ( n u m l i s t ) : r e s = 1 f o r n u m i n n u m l i s t : r e s * = n u m r e t u r n r e s p r i n t p r o d u c t ( [ 4 , 5 , 5 ] ) 78 / 121
79. Loops Practice Makes Perfect # 1 2 d e f r e m o v e _ d u p l i c a t e s ( v a r l i s t ) : n e w l i s t = [ ] f o r v a r i n v a r l i s t : i f v a r n o t i n n e w l i s t : n e w l i s t . a p p e n d ( v a r ) r e t u r n n e w l i s t p r i n t r e m o v e _ d u p l i c a t e s ( [ 1 , 1 , 2 , 2 ] ) # - - - # 1 3 s o r t e d ( ) # T h e m e d i a n i s t h e m i d d l e n u m b e r i n a s o r t e d s e q u e n c e o f n u m b e r s . I f y o u a r e g i v e n a s e q u e n c e w i t h # a n e v e n n u m b e r o f e l e m e n t s , y o u m u s t a v e r a g e t h e t w o e l e m e n t s s u r r o u n d i n g t h e m i d d l e . # s o r t e d ( [ 5 , 2 , 3 , 1 , 4 ] ) - - > [ 1 , 2 , 3 , 4 , 5 ] d e f m e d i a n ( v a r l i s t ) : s o r t e d l i s t = s o r t e d ( v a r l i s t ) l e n g t h = l e n ( v a r l i s t ) i f l e n g t h % 2 = = 1 : r e t u r n s o r t e d l i s t [ ( ( l e n g t h + 1 ) / 2 - 1 ) ] e l s e : r e t u r n ( s o r t e d l i s t [ l e n g t h / 2 - 1 ] + s o r t e d l i s t [ l e n g t h / 2 ] ) / 2 . 0 p r i n t m e d i a n ( [ 1 , 1 , 2 ] ) # 1 p r i n t m e d i a n ( [ 7 , 3 , 1 , 4 ] ) # 3 . 5 79 / 121
80. Exam Statistics (1) g r a d e s = [ 1 0 0 , 1 0 0 , 9 0 , 4 0 , 8 0 , 1 0 0 , 8 5 , 7 0 , 9 0 , 6 5 , 9 0 , 8 5 , 5 0 . 5 ] d e f p r i n t _ g r a d e s ( g r a d e s ) : f o r g r a d e i n g r a d e s : p r i n t g r a d e d e f g r a d e s _ s u m ( s c o r e s ) : t o t a l = 0 f o r s c o r e i n s c o r e s : t o t a l + = s c o r e r e t u r n t o t a l d e f g r a d e s _ a v e r a g e ( g r a d e s ) : r e t u r n g r a d e s _ s u m ( g r a d e s ) / f l o a t ( l e n ( g r a d e s ) ) p r i n t _ g r a d e s ( g r a d e s ) p r i n t g r a d e s _ s u m ( g r a d e s ) p r i n t g r a d e s _ a v e r a g e ( g r a d e s ) 80 / 121
81. Exam Statistics (2) d e f g r a d e s _ a v e r a g e ( g r a d e s ) : s u m _ o f _ g r a d e s = g r a d e s _ s u m ( g r a d e s ) a v e r a g e = s u m _ o f _ g r a d e s / f l o a t ( l e n ( g r a d e s ) ) r e t u r n a v e r a g e d e f g r a d e s _ v a r i a n c e ( s c o r e s ) : a v e r a g e = g r a d e s _ a v e r a g e ( s c o r e s ) v a r i a n c e = 0 f o r s c o r e i n s c o r e s : v a r i a n c e + = ( a v e r a g e - s c o r e ) * * 2 v a r i a n c e / = f l o a t ( l e n ( s c o r e s ) ) r e t u r n v a r i a n c e d e f g r a d e s _ s t d _ d e v i a t i o n ( v a r i a n c e ) : r e t u r n v a r i a n c e * * 0 . 5 v a r i a n c e = g r a d e s _ v a r i a n c e ( g r a d e s ) p r i n t p r i n t _ g r a d e s ( g r a d e s ) p r i n t g r a d e s _ s u m ( g r a d e s ) p r i n t g r a d e s _ a v e r a g e ( g r a d e s ) p r i n t g r a d e s _ v a r i a n c e ( g r a d e s ) p r i n t g r a d e s _ s t d _ d e v i a t i o n ( v a r i a n c e ) 81 / 121
82. Agenda 1. Python Syntax 2. Strings and Console Output 3. Conditionals and Control Flow 4. Functions 5. Lists and Dictionaries 6. Lists and Functions 7. Loops 8. Advanced Topics in Python 9. Introduction to Classes 10. File Input and Output 82 / 121
83. Advanced Topics in Python List Comprehensions m y _ d i c t = { " N a m e " : " O t o n g " , " A g e " : 2 3 , " T i t l e " : " D r " } p r i n t m y _ d i c t . i t e m s ( ) # [ ( ' A g e ' , 2 3 ) , ( ' N a m e ' , ' O t o n g ' ) , ( ' T i t l e ' , ' D r ' ) ] p r i n t m y _ d i c t . k e y s ( ) # [ ' A g e ' , ' N a m e ' , ' T i t l e ' ] p r i n t m y _ d i c t . v a l u e s ( ) # [ 2 3 , ' O t o n g ' , ' D r ' ] f o r k e y i n m y _ d i c t : p r i n t k e y , m y _ d i c t [ k e y ] # A g e 2 3 # N a m e O t o n g # T i t l e D r # Y o u s h o u l d u s e p r i n t a , b r a t h e r t h a n p r i n t a + " " + b What if we wanted to generate a list according to some logic—for example, a list of all the even numbers from 0 to 50? List comprehensions are a powerful way to generate lists using the for/in and if keywords 83 / 121
84. Advanced Topics in Python List Comprehensions # 1 e v e n s _ t o _ 5 0 = [ i f o r i i n r a n g e ( 5 1 ) i f i % 2 = = 0 ] p r i n t e v e n s _ t o _ 5 0 # [ 0 , 2 , 4 , 6 , 8 , 1 0 , 1 2 , 1 4 , 1 6 , 1 8 , 2 0 , 2 2 , 2 4 , 2 6 , 2 8 , 3 0 , 3 2 , 3 4 , 3 6 , 3 8 , 4 0 , 4 2 , 4 4 , 4 6 , 4 8 , 5 0 ] # - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - # 2 n e w _ l i s t = [ x f o r x i n r a n g e ( 1 , 6 ) ] # = > [ 1 , 2 , 3 , 4 , 5 ] d o u b l e s = [ x * 2 f o r x i n r a n g e ( 1 , 6 ) ] # = > [ 2 , 4 , 6 , 8 , 1 0 ] d o u b l e s _ b y _ 3 = [ x * 2 f o r x i n r a n g e ( 1 , 6 ) i f ( x * 2 ) % 3 = = 0 ] # = > [ 6 ] # - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - # 3 d o u b l e s _ b y _ 3 = [ x * 2 f o r x i n r a n g e ( 1 , 6 ) i f ( x * 2 ) % 3 = = 0 ] e v e n _ s q u a r e s = [ x * * 2 f o r x i n r a n g e ( 1 , 1 2 ) i f x % 2 = = 0 ] p r i n t e v e n _ s q u a r e s # [ 4 , 1 6 , 3 6 , 6 4 , 1 0 0 ] # - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 84 / 121
85. Advanced Topics in Python List Comprehensions # 4 c = [ ' C ' f o r x i n r a n g e ( 5 ) i f x < 3 ] p r i n t c # [ ' C ' , ' C ' , ' C ' ] # - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - # 5 c u b e s _ b y _ f o u r = [ x * * 3 f o r x i n r a n g e ( 1 , 1 1 ) i f ( x * * 3 ) % 4 = = 0 ] p r i n t c u b e s _ b y _ f o u r # [ 8 , 6 4 , 2 1 6 , 5 1 2 , 1 0 0 0 ] # - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - # 6 l = [ i * * 2 f o r i i n r a n g e ( 1 , 1 1 ) ] # S h o u l d b e [ 1 , 4 , 9 , 1 6 , 2 5 , 3 6 , 4 9 , 6 4 , 8 1 , 1 0 0 ] p r i n t l [ 2 : 9 : 2 ] # [ 9 , 2 5 , 4 9 , 8 1 ] - - 2 b e l a k a n g , 1 d i l o n c a t # l i s t s l i c i n g # [ s t a r t : e n d : s t r i d e ] # W h e r e s t a r t d e s c r i b e s w h e r e t h e s l i c e s t a r t s ( i n c l u s i v e ) , e n d i s w h e r e i t e n d s ( e x c l u s i v e ) , # a n d s t r i d e d e s c r i b e s t h e s p a c e b e t w e e n i t e m s i n t h e s l i c e d l i s t . F o r e x a m p l e , a s t r i d e o f 2 # w o u l d s e l e c t e v e r y o t h e r i t e m f r o m t h e o r i g i n a l l i s t t o p l a c e i n t h e s l i c e d l i s t . # s t a r t & e n d - - > i n d e x 85 / 121
86. Advanced Topics in Python List Comprehensions # 7 t o _ f i v e = [ ' A ' , ' B ' , ' C ' , ' D ' , ' E ' ] p r i n t t o _ f i v e [ 3 : ] # [ ' D ' , ' E ' ] p r i n t t o _ f i v e [ : 2 ] # [ ' A ' , ' B ' ] p r i n t t o _ f i v e [ : : 2 ] # [ ' A ' , ' C ' , ' E ' ] " " " T h e d e f a u l t s t a r t i n g i n d e x i s 0 . T h e d e f a u l t e n d i n g i n d e x i s t h e e n d o f t h e l i s t . T h e d e f a u l t s t r i d e i s 1 . " " " # - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - # 8 m y _ l i s t = r a n g e ( 1 , 1 1 ) # L i s t o f n u m b e r s 1 - 1 0 p r i n t m y _ l i s t [ : : 2 ] # [ 1 , 3 , 5 , 7 , 9 ] # - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 86 / 121
87. Advanced Topics in Python List Comprehensions # 9 l e t t e r s = [ ' A ' , ' B ' , ' C ' , ' D ' , ' E ' ] p r i n t l e t t e r s [ : : - 1 ] # [ ' E ' , ' D ' , ' C ' , ' B ' , ' A ' ] r i g h t t o l e f t # - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - # 1 0 m y _ l i s t = r a n g e ( 1 , 1 1 ) b a c k w a r d s = m y _ l i s t [ : : - 1 ] # - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - # 1 1 t o _ o n e _ h u n d r e d = r a n g e ( 1 0 1 ) b a c k w a r d s _ b y _ t e n s = t o _ o n e _ h u n d r e d [ : : - 1 0 ] p r i n t b a c k w a r d s _ b y _ t e n s # [ 1 0 0 , 9 0 , 8 0 , 7 0 , 6 0 , 5 0 , 4 0 , 3 0 , 2 0 , 1 0 , 0 ] # - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - # 1 2 t o _ 2 1 = r a n g e ( 1 , 2 2 ) o d d s = t o _ 2 1 [ : : 2 ] m i d d l e _ t h i r d = t o _ 2 1 [ 7 : 1 4 ] 87 / 121
88. Advanced Topics in Python Lambda - Anonymous Function Functional programming : means that you're allowed to pass functions around just as if they were variables or values. The function the lambda creates is an anonymous function. Lambdas are useful when you need a quick function to do some work for you. When we pass the lambda to filter, filter uses the lambda to determine what to filter, and the second argument (my_list, which is just the numbers 0 – 15) is the list it does the filtering on. # e k i v a l e n l a m b d a x : x % 3 = = 0 d e f b y _ t h r e e ( x ) : r e t u r n x % 3 = = 0 # - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - # f i l t e r m y _ l i s t = r a n g e ( 1 6 ) p r i n t f i l t e r ( l a m b d a x : x % 3 = = 0 , m y _ l i s t ) # y g b s d i b a g i 3 - > [ 0 , 3 , 6 , 9 , 1 2 , 1 5 ] # - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 88 / 121
89. Advanced Topics in Python Lambda - Anonymous Function l a n g u a g e s = [ " H T M L " , " J a v a S c r i p t " , " P y t h o n " , " R u b y " ] p r i n t f i l t e r ( l a m b d a x : x = = " P y t h o n " , l a n g u a g e s ) # [ ' P y t h o n ' ] # - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - c u b e s = [ x * * 3 f o r x i n r a n g e ( 1 , 1 1 ) ] p r i n t f i l t e r ( l a m b d a x : x % 3 = = 0 , c u b e s ) # - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - s q u a r e s = [ x * * 2 f o r x i n r a n g e ( 1 , 1 1 ) ] p r i n t f i l t e r ( l a m b d a x : x > 3 0 a n d x < = 7 0 , s q u a r e s ) # [ 3 6 , 4 9 , 6 4 ] # - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 89 / 121
90. Advanced Topics in Python Recap # D i c t i o n a r y m o v i e s = { " M o n t y P y t h o n a n d t h e H o l y G r a i l " : " G r e a t " , " M o n t y P y t h o n ' s L i f e o f B r i a n " : " G o o d " , " M o n t y P y t h o n ' s M e a n i n g o f L i f e " : " O k a y " } p r i n t m o v i e s . i t e m s ( ) # f o r k e y i n m o v i e s : p r i n t k e y , m y _ d i c t [ k e y ] # - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - # C o m p r e h e n d i n g C o m p r e h e n s i o n s s q u a r e s = [ x * * 2 f o r x i n r a n g e ( 5 ) ] t h r e e s _ a n d _ f i v e s = [ x f o r x i n r a n g e ( 1 , 1 6 ) i f x % 3 = = 0 o r x % 5 = = 0 ] 90 / 121
91. Advanced Topics in Python Recap # L i s t S l i c i n g s t r = " A B C D E F G H I J " # s t r [ s t a r t : e n d : s t r i d e ] - > s t a r t , e n d , s t r i d e = 1 , 6 , 2 # - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - g a r b l e d = " ! X e X g X a X s X s X e X m X X t X e X r X c X e X s X X e X h X t X X m X a X X I " r e v _ g a r b l e d = g a r b l e d [ : : - 1 ] m e s s a g e = r e v _ g a r b l e d [ : : 2 ] p r i n t m e s s a g e # - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - # L a m b d a m y _ l i s t = r a n g e ( 1 6 ) p r i n t f i l t e r ( l a m b d a x : x % 3 = = 0 , m y _ l i s t ) g a r b l e d = " I X X X a X X m X a X X X n X o X X X X X t X h X e X X X X r X s X X X X e X c X X X r X e X t m X X e X s X X X s X a X X X X X X g X e X ! X X " m e s s a g e = f i l t e r ( l a m b d a x : x ! = ' X ' , g a r b l e d ) p r i n t m e s s a g e 91 / 121
92. Advanced Topics in Python Bitwise Operators # b i t w i s e o p e r a t o r p r i n t 5 > > 4 # R i g h t S h i f t 1 0 1 - > 0 p r i n t 5 < < 1 # L e f t S h i f t 1 0 1 - > 1 0 1 0 p r i n t 8 & 5 # B i t w i s e A N D 1 0 0 0 & 0 1 0 1 - > 0 p r i n t 9 | 4 # B i t w i s e O R p r i n t 1 2 ^ 4 2 # B i t w i s e X O R p r i n t ~ 8 8 # B i t w i s e N O T # 0 | 1 0 | 0 | 1 3 | 3 8 | - 8 9 # - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - # h a s i l o p e r a s i p r i n t - > d e s i m a l p r i n t 0 b 1 , # 1 p r i n t 0 b 1 0 , # 2 p r i n t 0 b 1 1 , # 3 p r i n t 0 b 1 0 0 , # 4 p r i n t 0 b 1 0 1 , # 5 p r i n t 0 b 1 1 0 , # 6 p r i n t 0 b 1 1 1 # 7 # 1 2 3 4 5 6 7 p r i n t 0 b 1 + 0 b 1 1 # 4 p r i n t 0 b 1 1 * 0 b 1 1 # 9 92 / 121
93. Advanced Topics in Python Bitwise Operators o n e = 0 b 1 ; t w o = 0 b 1 0 ; t h r e e = 0 b 1 1 ; f o u r = 0 b 1 0 0 ; f i v e = 0 b 1 0 1 ; s i x = 0 b 1 1 0 ; s e v e n = 0 b 1 1 1 ; e i g h t = 0 b 1 0 0 0 ; n i n e = 0 b 1 0 0 1 ; t e n = 0 b 1 0 1 0 ; e l e v e n = 0 b 1 0 1 1 ; t w e l v e = 0 b 1 1 0 0 p r i n t e i g h t # - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - p r i n t b i n ( 1 ) # 0 b 1 p r i n t b i n ( 2 ) # 0 b 1 0 p r i n t b i n ( 3 ) # 0 b 1 1 p r i n t b i n ( 4 ) # 0 b 1 0 0 p r i n t b i n ( 5 ) # 0 b 1 0 1 # - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - p r i n t i n t ( " 1 " , 2 ) # 1 p r i n t i n t ( " 1 0 " , 2 ) # 2 p r i n t i n t ( " 1 1 1 " , 2 ) # 7 p r i n t i n t ( " 0 b 1 0 0 " , 2 ) # 4 p r i n t i n t ( b i n ( 5 ) , 2 ) # 5 # P r i n t o u t t h e d e c i m a l e q u i v a l e n t o f t h e b i n a r y 1 1 0 0 1 0 0 1 . p r i n t i n t ( " 0 b 1 1 0 0 1 0 0 1 " , 2 ) # 2 0 1 # b a s e 2 s e m u a , p a k e i 0 b a t a u g a k , s a m a 93 / 121
94. Advanced Topics in Python Bitwise Operators s h i f t _ r i g h t = 0 b 1 1 0 0 s h i f t _ l e f t = 0 b 1 s h i f t _ r i g h t = s h i f t _ r i g h t > > 2 s h i f t _ l e f t = s h i f t _ l e f t < < 2 p r i n t b i n ( s h i f t _ r i g h t ) # 0 b 1 1 p r i n t b i n ( s h i f t _ l e f t ) # 0 b 1 0 0 # - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - p r i n t b i n ( 0 b 1 1 1 0 & 0 b 1 0 1 ) # 0 b 1 0 0 p r i n t b i n ( 0 b 1 1 1 0 | 0 b 1 0 1 ) # 0 b 1 1 1 1 p r i n t b i n ( 0 b 1 1 1 0 ^ 0 b 1 0 1 ) # x o r 0 b 1 0 1 1 # - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - p r i n t ~ 1 # - 2 p r i n t ~ 2 # - 3 p r i n t ~ 3 # - 4 p r i n t ~ 4 2 # - 4 3 p r i n t ~ 1 2 3 # - 1 2 4 # t h i s i s e q u i v a l e n t t o a d d i n g o n e t o t h e n u m b e r a n d t h e n m a k i n g i t n e g a t i v e . 94 / 121
95. Advanced Topics in Python Bitwise Operators # m a s k d e f c h e c k _ b i t 4 ( i n p u t ) : # i n p u t r e s e r v e d ? m a s k = 0 b 1 0 0 0 d e s i r e d = i n p u t & m a s k i f d e s i r e d > 0 : r e t u r n " o n " e l s e : r e t u r n " o f f " # - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - a = 0 b 1 0 1 1 1 0 1 1 m a s k = 0 b 1 0 0 p r i n t b i n ( a | m a s k ) # 0 b 1 0 1 1 1 1 1 1 p r i n t b i n ( a ^ m a s k ) # 0 b 1 0 1 1 1 1 1 1 # - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - a = 0 b 1 1 1 0 1 1 1 0 m a s k = 0 b 1 1 1 1 1 1 1 1 # f l i p * s e m u a * b i t a p r i n t b i n ( a ^ m a s k ) # 0 b 1 0 0 0 1 # - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - d e f f l i p _ b i t ( n u m b e r , n ) : m a s k = ( 0 b 1 < < ( n - 1 ) ) r e s u l t = n u m b e r ^ m a s k r e t u r n b i n ( r e s u l t ) # x o r k a l a u m a s k 1 n g e - f l i p ; k a l o m a s k 0 t e t a p 95 / 121
96. Agenda 1. Python Syntax 2. Strings and Console Output 3. Conditionals and Control Flow 4. Functions 5. Lists and Dictionaries 6. Lists and Functions 7. Loops 8. Advanced Topics in Python 9. Introduction to Classes 10. File Input and Output 96 / 121
97. Introduction to Classes Python is an object-oriented programming language, which means it manipulates programming constructs called objects. You can think of an object as a single data structure that contains data as well as functions; functions of objects are called methods. c l a s s F r u i t ( o b j e c t ) : " " " A c l a s s t h a t m a k e s v a r i o u s t a s t y f r u i t s . " " " d e f _ _ i n i t _ _ ( s e l f , n a m e , c o l o r , f l a v o r , p o i s o n o u s ) : s e l f . n a m e = n a m e s e l f . c o l o r = c o l o r s e l f . f l a v o r = f l a v o r s e l f . p o i s o n o u s = p o i s o n o u s d e f d e s c r i p t i o n ( s e l f ) : p r i n t " I ' m a % s % s a n d I t a s t e % s . " % ( s e l f . c o l o r , s e l f . n a m e , s e l f . f l a v o r ) d e f i s _ e d i b l e ( s e l f ) : i f n o t s e l f . p o i s o n o u s : p r i n t " Y e p ! I ' m e d i b l e . " e l s e : p r i n t " D o n ' t e a t m e ! I a m s u p e r p o i s o n o u s . " # - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - l e m o n = F r u i t ( " l e m o n " , " y e l l o w " , " s o u r " , F a l s e ) l e m o n . d e s c r i p t i o n ( ) l e m o n . i s _ e d i b l e ( ) 97 / 121
98. Introduction to Classes p a s s doesn't do anything, but it's useful as a placeholder in areas of your code where Python expects an expression _ _ i n i t _ _ ( ) function is required for classes, and it's used to initialize the objects it creates. _ _ i n i t _ _ ( ) always takes at least one argument, s e l f , that refers to the object being created. You can think of _ _ i n i t _ _ ( ) as the function that "boots up" each object the class creates. We can access attributes of our objects using dot notation c l a s s A n i m a l ( o b j e c t ) : p a s s c l a s s A n i m a l ( o b j e c t ) : d e f _ _ i n i t _ _ ( s e l f ) : p a s s c l a s s A n i m a l ( o b j e c t ) : d e f _ _ i n i t _ _ ( s e l f , n a m e ) : s e l f . n a m e = n a m e z e b r a = A n i m a l ( " J e f f r e y " ) p r i n t z e b r a . n a m e # - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - c l a s s S q u a r e ( o b j e c t ) : d e f _ _ i n i t _ _ ( s e l f ) : s e l f . s i d e s = 4 m y _ s h a p e = S q u a r e ( ) p r i n t m y _ s h a p e . s i d e s 98 / 121
99. Introduction to Classes c l a s s A n i m a l ( o b j e c t ) : " " " M a k e s c u t e a n i m a l s . " " " d e f _ _ i n i t _ _ ( s e l f , n a m e , a g e , i s _ h u n g r y ) : s e l f . n a m e = n a m e s e l f . a g e = a g e s e l f . i s _ h u n g r y = i s _ h u n g r y # N o t e t h a t s e l f i s o n l y u s e d i n t h e _ _ i n i t _ _ ( ) f u n c t i o n * d e f i n i t i o n * ; # w e d o n ' t n e e d t o p a s s i t t o o u r i n s t a n c e o b j e c t s . z e b r a = A n i m a l ( " J e f f r e y " , 2 , T r u e ) g i r a f f e = A n i m a l ( " B r u c e " , 1 , F a l s e ) p a n d a = A n i m a l ( " C h a d " , 7 , T r u e ) p r i n t z e b r a . n a m e , z e b r a . a g e , z e b r a . i s _ h u n g r y # J e f f r e y 2 T r u e p r i n t g i r a f f e . n a m e , g i r a f f e . a g e , g i r a f f e . i s _ h u n g r y # B r u c e 1 F a l s e p r i n t p a n d a . n a m e , p a n d a . a g e , p a n d a . i s _ h u n g r y # C h a d 7 T r u e 99 / 121
100. Introduction to Classes Class Scope Another important aspect of Python classes is scope. The scope of a variable is the context in which it's visible to the program. It may surprise you to learn that not all variables are accessible to all parts of a Python program at all times. When dealing with classes, you can have variables that are available everywhere (global variables), variables that are only available to members of a certain class (member variables), and variables that are only available to particular instances of a class (instance variables). 100 / 121
101. Introduction to Classes Class Scope variables: global, member, instance c l a s s A n i m a l ( o b j e c t ) : " " " M a k e s c u t e a n i m a l s . " " " i s _ a l i v e = T r u e d e f _ _ i n i t _ _ ( s e l f , n a m e , a g e ) : s e l f . n a m e = n a m e s e l f . a g e = a g e z e b r a = A n i m a l ( " J e f f r e y " , 2 ) g i r a f f e = A n i m a l ( " B r u c e " , 1 ) p a n d a = A n i m a l ( " C h a d " , 7 ) p r i n t z e b r a . n a m e , z e b r a . a g e , z e b r a . i s _ a l i v e # J e f f r e y 2 T r u e p r i n t g i r a f f e . n a m e , g i r a f f e . a g e , g i r a f f e . i s _ a l i v e # B r u c e 1 T r u e p r i n t p a n d a . n a m e , p a n d a . a g e , p a n d a . i s _ a l i v e # C h a d 7 T r u e # i s _ a l i v e m e m b e r v a r i a b l e ; n a m e , a g e i n s t a n c e v a r i a b l e s 101 / 121
102. Introduction to Classes Class Scope c l a s s A n i m a l ( o b j e c t ) : i s _ a l i v e = T r u e d e f _ _ i n i t _ _ ( s e l f , n a m e , a g e ) : s e l f . n a m e = n a m e s e l f . a g e = a g e d e f d e s c r i p t i o n ( s e l f ) : p r i n t s e l f . n a m e p r i n t s e l f . a g e h i p p o = A n i m a l ( " N i l " , 5 ) h i p p o . d e s c r i p t i o n ( ) # - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - h i p p o = A n i m a l ( " J a k e " , 1 2 ) c a t = A n i m a l ( " B o o t s " , 3 ) p r i n t h i p p o . i s _ a l i v e # T r u e h i p p o . i s _ a l i v e = F a l s e p r i n t h i p p o . i s _ a l i v e # F a l s e p r i n t c a t . i s _ a l i v e # T r u e 102 / 121
103. Introduction to Classes Class Scope c l a s s A n i m a l ( o b j e c t ) : i s _ a l i v e = T r u e h e a l t h = " g o o d " d e f _ _ i n i t _ _ ( s e l f , n a m e , a g e ) : s e l f . n a m e = n a m e s e l f . a g e = a g e d e f d e s c r i p t i o n ( s e l f ) : p r i n t s e l f . n a m e p r i n t s e l f . a g e h i p p o = A n i m a l ( " N i l " , 5 ) h i p p o . d e s c r i p t i o n ( ) s l o t h = A n i m a l ( " s l o t h N a m e " , 6 ) o c e l o t = A n i m a l ( " o c e l o t N a m e " , 7 ) p r i n t h i p p o . h e a l t h # g o o d p r i n t s l o t h . h e a l t h # g o o d p r i n t o c e l o t . h e a l t h # g o o d # m e m b e r v a r i a b l e = c l a s s v a r i a b l e ( b u k a n i n s t a n c e , a v a i l a b l e t o a l l i n s t ) 103 / 121
104. Introduction to Classes Class Scope c l a s s S h o p p i n g C a r t ( o b j e c t ) : " " " C r e a t e s s h o p p i n g c a r t o b j e c t s f o r u s e r s o f o u r f i n e w e b s i t e . " " " i t e m s _ i n _ c a r t = { } d e f _ _ i n i t _ _ ( s e l f , c u s t o m e r _ n a m e ) : s e l f . c u s t o m e r _ n a m e = c u s t o m e r _ n a m e d e f a d d _ i t e m ( s e l f , p r o d u c t , p r i c e ) : " " " A d d p r o d u c t t o t h e c a r t . " " " i f n o t p r o d u c t i n s e l f . i t e m s _ i n _ c a r t : s e l f . i t e m s _ i n _ c a r t [ p r o d u c t ] = p r i c e p r i n t p r o d u c t + " a d d e d . " e l s e : p r i n t p r o d u c t + " i s a l r e a d y i n t h e c a r t . " d e f r e m o v e _ i t e m ( s e l f , p r o d u c t ) : " " " R e m o v e p r o d u c t f r o m t h e c a r t . " " " i f p r o d u c t i n s e l f . i t e m s _ i n _ c a r t : d e l s e l f . i t e m s _ i n _ c a r t [ p r o d u c t ] p r i n t p r o d u c t + " r e m o v e d . " e l s e : p r i n t p r o d u c t + " i s n o t i n t h e c a r t . " 104 / 121
105. Introduction to Classes Class Scope m y _ c a r t 1 = S h o p p i n g C a r t ( " O t o n g " ) m y _ c a r t 2 = S h o p p i n g C a r t ( " U d j a n g " ) m y _ c a r t 1 . a d d _ i t e m ( " O b e n g " , 2 0 0 0 ) # O b e n g a d d e d . m y _ c a r t 1 . a d d _ i t e m ( " O b e n g " , 1 0 0 0 ) # O b e n g i s a l r e a d y i n t h e c a r t . p r i n t m y _ c a r t 1 . i t e m s _ i n _ c a r t # { ' O b e n g ' : 2 0 0 0 } m y _ c a r t 2 . a d d _ i t e m ( " S a p u " , 2 0 0 0 ) # S a p u a d d e d . m y _ c a r t 2 . a d d _ i t e m ( " S a p u " , 1 0 0 0 ) # S a p u i s a l r e a d y i n t h e c a r t . p r i n t m y _ c a r t 2 . i t e m s _ i n _ c a r t # { ' O b e n g ' : 2 0 0 0 , ' S a p u ' : 2 0 0 0 } m y _ c a r t 1 . a d d _ i t e m ( " S a p u " , 5 0 0 0 ) # S a p u i s a l r e a d y i n t h e c a r t . p r i n t m y _ c a r t 1 . i t e m s _ i n _ c a r t # { ' O b e n g ' : 2 0 0 0 , ' S a p u ' : 2 0 0 0 } m y _ c a r t 2 . i t e m s _ i n _ c a r t = { ' B u k u ' : 3 0 0 0 } p r i n t m y _ c a r t 2 . i t e m s _ i n _ c a r t # { ' B u k u ' : 3 0 0 0 } p r i n t m y _ c a r t 1 . i t e m s _ i n _ c a r t # { ' O b e n g ' : 2 0 0 0 , ' S a p u ' : 2 0 0 0 } m y _ c a r t 2 . a d d _ i t e m ( " S a p u " , 1 0 0 0 ) # S a p u a d d e d . p r i n t m y _ c a r t 2 . i t e m s _ i n _ c a r t # { ' S a p u ' : 1 0 0 0 , ' B u k u ' : 3 0 0 0 } m y _ c a r t 1 . a d d _ i t e m ( " D o d o l " , 1 0 0 0 0 ) # D o d o l a d d e d . p r i n t m y _ c a r t 1 . i t e m s _ i n _ c a r t # { ' O b e n g ' : 2 0 0 0 , ' S a p u ' : 2 0 0 0 , ' D o d o l ' : 1 0 0 0 0 } p r i n t m y _ c a r t 2 . i t e m s _ i n _ c a r t # { ' S a p u ' : 1 0 0 0 , ' B u k u ' : 3 0 0 0 } 105 / 121
106. Introduction to Classes Classes can be very useful for storing complicated objects with their own methods and variables. Defining a class is much like defining a function, but we use the class keyword instead. We also use the word object in parentheses because we want our classes to inherit the object class. This means that our class has all the properties of an object, which is the simplest, most basic class. Later we'll see that classes can inherit other, more complicated classes. Notes for Variables: To create instance variables, initialize them in the init function When Python sees self.X (object.X) it looks if there's a property X in your object, and if there is none, it looks at its class. 106 / 121
107. Introduction to Classes Inheritance Inheritance is the process by which one class takes on the attributes and methods of another, and it's used to express an is-a relationship. For example, a Panda is a bear, so a Panda class could inherit from a Bear class. c l a s s C u s t o m e r ( o b j e c t ) : " " " P r o d u c e s o b j e c t s t h a t r e p r e s e n t c u s t o m e r s . " " " d e f _ _ i n i t _ _ ( s e l f , c u s t o m e r _ i d ) : s e l f . c u s t o m e r _ i d = c u s t o m e r _ i d d e f d i s p l a y _ c a r t ( s e l f ) : p r i n t " I ' m a s t r i n g t h a t s t a n d s i n f o r t h e c o n t e n t s o f y o u r s h o p p i n g c a r t ! " c l a s s R e t u r n i n g C u s t o m e r ( C u s t o m e r ) : " " " F o r c u s t o m e r s o f t h e r e p e a t v a r i e t y . " " " d e f d i s p l a y _ o r d e r _ h i s t o r y ( s e l f ) : p r i n t " I ' m a s t r i n g t h a t s t a n d s i n f o r y o u r o r d e r h i s t o r y ! " m o n t y _ p y t h o n = R e t u r n i n g C u s t o m e r ( " I D : 1 2 3 4 5 " ) m o n t y _ p y t h o n . d i s p l a y _ c a r t ( ) # C u s t o m e r . d i s p l a y _ c a r t m o n t y _ p y t h o n . d i s p l a y _ o r d e r _ h i s t o r y ( ) # R e t u r n i n g C u s t o m e r 107 / 121
108. Introduction to Classes Inheritance c l a s s S h a p e ( o b j e c t ) : " " " M a k e s s h a p e s ! " " " d e f _ _ i n i t _ _ ( s e l f , n u m b e r _ o f _ s i d e s ) : s e l f . n u m b e r _ o f _ s i d e s = n u m b e r _ o f _ s i d e s c l a s s T r i a n g l e ( S h a p e ) : d e f _ _ i n i t _ _ ( s e l f , s i d e 1 , s i d e 2 , s i d e 3 ) : s e l f . s i d e 1 = s i d e 1 s e l f . s i d e 2 = s i d e 2 s e l f . s i d e 3 = s i d e 3 # O v e r r i d e _ _ i n i t _ _ s e g i t i g a 2 = T r i a n g l e ( 1 , 2 , 3 ) p r i n t s e g i t i g a 2 . s i d e 1 # p r i n t s e g i t i g a 2 . n u m b e r _ o f _ s i d e s # s u p e r ? 108 / 121
109. Introduction to Classes Inheritance c l a s s E m p l o y e e ( o b j e c t ) : d e f _ _ i n i t _ _ ( s e l f , n a m e ) : s e l f . n a m e = n a m e d e f g r e e t ( s e l f , o t h e r ) : p r i n t " H e l l o , % s " % o t h e r . n a m e c l a s s C E O ( E m p l o y e e ) : d e f g r e e t ( s e l f , o t h e r ) : p r i n t " G e t b a c k t o w o r k , % s ! " % o t h e r . n a m e c e o = C E O ( " E m i l y " ) e m p = E m p l o y e e ( " S t e v e " ) e m p . g r e e t ( c e o ) # H e l l o , E m i l y c e o . g r e e t ( e m p ) # G e t b a c k t o w o r k , S t e v e ! 109 / 121
110. Introduction to Classes Inheritance Sometimes you'll want one class that inherits from another to not only take on the methods and attributes of its parent, but to override one or more of them. On the flip side, sometimes you'll be working with a derived class (or subclass) and realize that you've overwritten a method or attribute defined in that class' base class (also called a parent or superclass) that you actually need. Have no fear! You can directly access the attributes or methods of a superclass with Python's built-in super call. 110 / 121
111. Introduction to Classes Inheritance c l a s s E m p l o y e e ( o b j e c t ) : " " " M o d e l s r e a l - l i f e e m p l o y e e s ! " " " d e f _ _ i n i t _ _ ( s e l f , e m p l o y e e _ n a m e ) : s e l f . e m p l o y e e _ n a m e = e m p l o y e e _ n a m e d e f c a l c u l a t e _ w a g e ( s e l f , h o u r s ) : s e l f . h o u r s = h o u r s r e t u r n h o u r s * 2 0 . 0 0 c l a s s P a r t T i m e E m p l o y e e ( E m p l o y e e ) : d e f c a l c u l a t e _ w a g e ( s e l f , h o u r s ) : s e l f . h o u r s = h o u r s r e t u r n h o u r s * 1 2 . 0 0 d e f f u l l _ t i m e _ w a g e ( s e l f , h o u r s ) : r e t u r n s u p e r ( P a r t T i m e E m p l o y e e , s e l f ) . c a l c u l a t e _ w a g e ( h o u r s ) m i l t o n = P a r t T i m e E m p l o y e e ( " M i l t o n " ) p r i n t m i l t o n . f u l l _ t i m e _ w a g e ( 1 0 ) 111 / 121
112. Introduction to Classes c l a s s T r i a n g l e ( o b j e c t ) : n u m b e r _ o f _ s i d e s = 3 d e f _ _ i n i t _ _ ( s e l f , a n g l e 1 , a n g l e 2 , a n g l e 3 ) : s e l f . a n g l e 1 = a n g l e 1 s e l f . a n g l e 2 = a n g l e 2 s e l f . a n g l e 3 = a n g l e 3 d e f c h e c k _ a n g l e s ( s e l f ) : s u m _ a n g l e = s e l f . a n g l e 1 + s e l f . a n g l e 2 + s e l f . a n g l e 3 i f s u m _ a n g l e = = 1 8 0 : r e t u r n T r u e e l s e : r e t u r n F a l s e c l a s s E q u i l a t e r a l ( T r i a n g l e ) : a n g l e = 6 0 d e f _ _ i n i t _ _ ( s e l f ) : s e l f . a n g l e 1 = s e l f . a n g l e s e l f . a n g l e 2 = s e l f . a n g l e s e l f . a n g l e 3 = s e l f . a n g l e m y _ t r i a n g l e = T r i a n g l e ( 9 0 , 3 0 , 6 0 ) p r i n t m y _ t r i a n g l e . n u m b e r _ o f _ s i d e s # 3 i n h e r i t e d p r i n t m y _ t r i a n g l e . c h e c k _ a n g l e s ( ) # T r u e 112 / 121
113. Introduction to Classes c l a s s C a r ( o b j e c t ) : c o n d i t i o n = " n e w " d e f _ _ i n i t _ _ ( s e l f , m o d e l , c o l o r , m p g ) : s e l f . m o d e l = m o d e l ; s e l f . c o l o r = c o l o r ; s e l f . m p g = m p g d e f d i s p l a y _ c a r ( s e l f ) : r e t u r n " T h i s i s a % s % s w i t h % s M P G . " % ( s e l f . c o l o r , s e l f . m o d e l , s t r ( s e l f . m p g ) ) d e f d r i v e _ c a r ( s e l f ) : s e l f . c o n d i t i o n = " u s e d " c l a s s E l e c t r i c C a r ( C a r ) : d e f _ _ i n i t _ _ ( s e l f , m o d e l , c o l o r , m p g , b a t t e r y _ t y p e ) : s u p e r ( E l e c t r i c C a r , s e l f ) . _ _ i n i t _ _ ( m o d e l , c o l o r , m p g ) s e l f . b a t t e r y _ t y p e = b a t t e r y _ t y p e d e f d r i v e _ c a r ( s e l f ) : s e l f . c o n d i t i o n = " l i k e n e w " m y _ c a r = E l e c t r i c C a r ( " D e L o r e a n " , " s i l v e r " , 8 8 , " m o l t e n s a l t " ) p r i n t m y _ c a r . c o n d i t i o n # n e w m y _ c a r . d r i v e _ c a r ( ) # p r i n t m y _ c a r . c o n d i t i o n # l i k e n e w m y _ c a r 1 = C a r ( " D e L o r e a n " , " s i l v e r " , 8 8 ) p r i n t m y _ c a r 1 . c o n d i t i o n # n e w p r i n t m y _ c a r 1 . m o d e l # D e L o r e a n p r i n t m y _ c a r 1 . d i s p l a y _ c a r ( ) # T h i s i s a s i l v e r D e L o r e a n w i t h 8 8 M P G . m y _ c a r 1 . d r i v e _ c a r ( ) p r i n t m y _ c a r 1 . c o n d i t i o n # u s e d 113 / 121
114. Introduction to Classes Usually, classes are most useful for holding and accessing abstract collections of data. One useful class method to override is the built-in _ _ r e p r _ _ ( ) method, which is short for representation; by providing a return value in this method, we can tell Python how to represent an object of our class (for instance, when using a print statement). c l a s s P o i n t 3 D ( o b j e c t ) : d e f _ _ i n i t _ _ ( s e l f , x , y , z ) : s e l f . x = x s e l f . y = y s e l f . z = z d e f _ _ r e p r _ _ ( s e l f ) : r e t u r n " ( % d , % d , % d ) " % ( s e l f . x , s e l f . y , s e l f . z ) m y _ p o i n t = P o i n t 3 D ( 1 , 2 , 3 ) p r i n t m y _ p o i n t # ( 1 , 2 , 3 ) 114 / 121
115. Agenda 1. Python Syntax 2. Strings and Console Output 3. Conditionals and Control Flow 4. Functions 5. Lists and Dictionaries 6. Lists and Functions 7. Loops 8. Advanced Topics in Python 9. Introduction to Classes 10. File Input and Output 115 / 121
116. File Input and Output Built-in io functions Write # G e n e r a t e s a l i s t o f s q u a r e s o f t h e n u m b e r s 1 - 1 0 m y _ l i s t = [ i * * 2 f o r i i n r a n g e ( 1 , 1 1 ) ] f = o p e n ( " o u t p u t . t x t " , " w " ) f o r i t e m i n m y _ l i s t : f . w r i t e ( s t r ( i t e m ) + " \ n " ) f . c l o s e ( ) # T h i s t o l d P y t h o n t o o p e n o u t p u t . t x t i n " w " m o d e ( " w " s t a n d s f o r " w r i t e " ) . # W e s t o r e d t h e r e s u l t o f t h i s o p e r a t i o n i n a f i l e o b j e c t , f . 116 / 121
117. File Input and Output Write m y _ l i s t = [ i * * 2 f o r i i n r a n g e ( 1 , 1 1 ) ] m y _ f i l e = o p e n ( " o u t p u t . t x t " , " r + " ) f o r i i n m y _ l i s t : m y _ f i l e . w r i t e ( s t r ( i ) + " \ n " ) m y _ f i l e . c l o s e ( ) # " r + " a s a s e c o n d a r g u m e n t t o t h e f u n c t i o n s o t h e # f i l e w i l l a l l o w y o u t o r e a d a n d w r i t e 117 / 121
118. File Input and Output Read m y _ f i l e = o p e n ( " o u t p u t . t x t " , " r " ) p r i n t m y _ f i l e . r e a d ( ) m y _ f i l e . c l o s e ( ) # - - - # i f w e w a n t t o r e a d f r o m a f i l e l i n e b y l i n e , # r a t h e r t h a n p u l l i n g t h e e n t i r e f i l e i n a t o n c e . m y _ f i l e = o p e n ( " t e x t . t x t " , " r " ) p r i n t m y _ f i l e . r e a d l i n e ( ) p r i n t m y _ f i l e . r e a d l i n e ( ) p r i n t m y _ f i l e . r e a d l i n e ( ) m y _ f i l e . c l o s e ( ) 118 / 121
119. File Input and Output During the I/O process, data is buffered: this means that it is held in a temporary location before being written to the file. Python doesn't flush the buffer—that is, write data to the file—until it's sure you're done writing. One way to do this is to close the file. If you write to a file without closing, the data won't make it to the target file. # O p e n t h e f i l e f o r r e a d i n g r e a d _ f i l e = o p e n ( " t e x t . t x t " , " r " ) # U s e a s e c o n d f i l e h a n d l e r t o o p e n t h e f i l e f o r w r i t i n g w r i t e _ f i l e = o p e n ( " t e x t . t x t " , " w " ) # W r i t e t o t h e f i l e w r i t e _ f i l e . w r i t e ( " N o t c l o s i n g f i l e s i s V E R Y B A D . " ) w r i t e _ f i l e . c l o s e ( ) # T r y t o r e a d f r o m t h e f i l e p r i n t r e a d _ f i l e . r e a d ( ) r e a d _ f i l e . c l o s e ( ) 119 / 121
120. File Input and Output File objects contain a special pair of built-in methods: _ _ e n t e r _ _ ( ) and _ _ e x i t _ _ ( ) . The details aren't important, but what is important is that when a file object's _ _ e x i t _ _ ( ) method is invoked, it automatically closes the file. How do we invoke this method? With with and as. w i t h o p e n ( " t e x t . t x t " , " w " ) a s t e x t f i l e : t e x t f i l e . w r i t e ( " S u c c e s s ! " ) # g a k p e r l u c l o s e , c l o s e a u t o m a t i c a l l y # - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - f = o p e n ( " b g . t x t " ) f . c l o s e d # F a l s e f . c l o s e ( ) f . c l o s e d # T r u e # - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - w i t h o p e n ( " t e x t . t x t " , " w " ) a s m y _ f i l e : m y _ f i l e . w r i t e ( " o t o n g " ) ; i f m y _ f i l e . c l o s e d = = F a l s e : m y _ f i l e . c l o s e ( ) p r i n t m y _ f i l e . c l o s e d 120 / 121
121. Python - An Introduction END Eueung Mulyana | http://eueung.github.io/EL6240/py based on the material @Codecademy Attribution-ShareAlike CC BY-SA 121 / 121