Python - An Introduction Eueung Mulyana | http://eueung.github.io/EL6240/py based on the material @Codecademy Attribution-ShareAlike CC BY-SA 1 / 121 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

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 

Python - An Introduction END Eueung Mulyana | http://eueung.github.io/EL6240/py based on the material @Codecademy Attribution-ShareAlike CC BY-SA 121 / 121