Python - Intro to programming

Transcript

1. Intro to Programming With Python
2. Computer Program - A computer program is a set of instructions that causes a computer to perform some kind of action. - Software, not hardware
3. What is programming? It’s just the process of writing computer programs.
4. Activity: Directions How would you direct me to throw this piece of paper into the trash?
5. Normally… - You need another program to write your program in - And download a ton of other things - But we’ll don’t have to worry about it
6. Hello World! https://www.tutorialspoint.com/execute_python_online.php print("Hello world!")
7. About Python - Created by Guido van Rossum - Named after the BBC TV Show “Monty Python’s Flying Circus” - Simple and minimalistic compared to other programs - It’s almost like English - Free and Open Sourced - Powerful
8. Vocabulary
9. Pseudocode - Not real code - Images, diagrams, or writing that describe code - Help you figure out what you want to code without real code
10. Syntax - Lower case (it matters) - Start on a new line every time you write a new step - For every block of code that is related to one step, you should indent and start a new line - All of this also help keep your code neat
11. Variable - Describes a place to store information such as numbers, text, lists of numbers and text, and etc. - Has a name that you give it - Must be unique - It’s like a labeled box that is used to contain other stuff
12. https://codecombat.com/students?_cc=F ireEyeCoin
13. Naming Variables - Variables names can contain only letters, numbers, and underscore. - Cannot start with a number - Spaces are not allowed - Use underscore instead - Do not use python keywords and function names as variable names - Variable names should be short but descriptive
14. String - Refers to that bit of text you want to display to someone. - Ex. print(Hello World!) - Hello world! is the String - You can have an empty String - 0 characters but it exist - Position # of a String - Hello World - H = 0 - d = 10 - Space = 5
15. Variable Activity https://www.tutorialspoint.com/execute_python_online.php Put things in variables and print them out! - variable_name = “message” - print(variable_name)
16. What do you get?
17. Strings cat = cats are domesticated felines print(cat) What did you get when you forget the quotations?
18. Syntax error - SyntaxError means you made a mistake in the arrangement and order of words in your code - You did something Python did not expect - EOL means end-of-line - Your program stopped at the end of the line and did not find a double quote to close the string Try and see what other errors you can get by messing up the syntax
19. Multiline String
20. Printing a variable and a string • Try printing out a string stored in a variable with another string - greeting = “Hello” - print(greeting + “ Vina!”)
21. Make your own variables (Mad Libs) Store Strings in the follow variable names: • my_name • adjective_1 • emotion • memory • plural_noun_1 • adjective_2 • plural_noun_2 • something_delicious • something_yucky • adjective_3 • noun
22. Make your computer print this with the corresponding variable name print(“My name is ” + your_name + “and…
23. Calculation
24. Operators Basic symbols used by Python to perform mathematical operations
25. Order of Operations - Basic Math - PEMDAS - Parentheses first, exponents, multiply, divide, add, subtract
26. Calculate these: record your answers 1. 5 + 30 * 20 2. (5 + 30) * 20 3. (5 + 30) * 20 / 10 4. 6 + 34 * 15 / 8 5. 6 + 34 * 15.0 / 8 Print(5 + 30 * 20) Print((5 + 30) * 20)
27. Variables - Try making variables and assigning values
28. Answer these problems (see if you can solve these yourself) Bob = 100, Anna = 5, kyle = 39 1. Bob - 32 + Anna = ? 2. Anna - Kyle = ? 3. Bob + Anna + Kyle ?
29. Decimals - If you don’t have a decimal on the left side of your equation, you won’t get a decimal answer. - It never rounds up or down. It Truncates your number 0.7 = ? 2.4 = ? 7.943 =? 43.0 = ?
30. Be careful In Python and most other computer languages • 3/2 = 1 • 3.0 / 2 = 1.5
31. Print a String and a integer on the same line • Example: Bob = 100 • print(“Bob = 100”) • Or • bob = 100 ß the variable you already stored • print(“Bob had this amount of money =“ + str(bob)) ◦ turns your number into a string
32. Embedding Values in String Now combine number variables and string variables together in a sentence - You can use this : %s - This acts like an marker for a value you want to add later
33. More math functions • ** (exponents) • % (find remainder) 2^2 = 4 Python code: 2**2 = 4 Python code: 10 % 3 = 1
34. More math functions (for fun) • abs(x) • min(x) • max(x) • pow(x) ◦ pow(2 , 2) ◦ 2**2 • sum(x) ◦ sum( 1, 2 , 3 , 4 )
35. Defining Functions
36. Functions • Just like variables • You’re storing steps into a container (called functions) • You can name them too, just like the way you name variables
37. For example • 1. def function_name(x) • 2. return what you want the function to do • 2. print the result
38. Cont. • Notice the indentation. We’re grouping statements together. • What are some functions we already know and used? ◦ Hint: these are already created and saved into Python language library
39. Where can we use it? • If you need to calculate a math equation over and over again • Ex. Finding the area of many different rectangles from a list: ◦ Math problem: Find the area of the following rectangles 5 by 5 6 by 8 150 by 93 43 by 29.3 Def area(x, y) : return x*y
40. Try it out! • Write a function to find the area of a triangle given 2 numbers (height and base) • See if you get the correct answer if height = 15 , base = 4.3
41. Answer def triangle_area(x, y): return x*y/2 print(triangle_area(15, 4.3)) Equals 32.25
42. Congratulations! You know enough coding for you write a program to get your computer to do your math homework for you! (most practical for a series of problems requiring the same formula)
43. Lists
44. Lists • Allows you to store sets of information in one place, whether you have just a few items or millions of items ◦ Can put strings, numbers, a lot of things ◦ You can name them too like how you name variables ▪ Name them pural words like bicycles, cats, dogs • Very important. Will use list a lot in coding
45. Code for lists • Just like making a variable, except you use [‘…. ‘ , ‘…. ‘ ] • Example: ◦ Writing an variable: ▪ bicycle = “trek” ◦ Writing a list: ▪ bicycle = [‘trek’, ‘cannondale’ , ‘redline’ , ‘pedal’]
46. Write your own list • listname = [ ‘blahblahblah’, ‘blahblah’, ‘baljfkdla’ ] • print(listname)
47. Numbers in a list • If you have a list that contains numbers, you don’t need the quotations • List of strings need “ ” List1 = [1, 2, 3, 4] - You can also multiply a list by a number. Try multiplying list1 by 5 and print it out
48. answer • list1=[1, 2] • print(list1 * 5) • [1, 2, 1, 2, 1, 2 ,1, 2, 1, 2] • So you can’t use +, /, or – to a list like we just did with * • Why? Because the computer is dumb
49. Tuples • Is like a list that uses parentheses • You should of noticed by now that lists use brackets [ ] • You cannot change a tuple once you created it ◦ A list you can change it
50. Elements • They are the things that you stored in a list • bicycle = [‘trek’, ‘cannondale’ , ‘redline’ , ‘pedal’] ◦ Trek, cannondale, redline, pedal are the elements
51. Index positions • When you store something into a list, it has a positions number • The position number starts at 0 ◦ Usually the case for most programming languages bicycle = [‘trek’, ‘cannondale’ , ‘redline’ , ‘pedal’] If you want to print the first element in the list, you would do this: print(list_name [ the number ]) print(bicycle[0])
52. Create your own list and print the third element • Make a list of names • Print the 3rd name on your list • Also print “The third person’s name is ” before the name, on the same line ◦ Bonus if you store the previous message as a variable before you printed it
53. Special Case, what do you get? • With your previous list, try printing the element with the index of [-1] • Example ◦ print (bicycles[-1] )
54. Debugging • Debugging refers to finding mistakes in your code • Back in the days, computers looked like this: • Admiral Grace Hopper, while working on a computer like this, found a moth stuck inside which caused the computer to not work - called it “debugging” the system - the term caught on
55. When ever your code is doing something unexpected… • You need to debug • Use Print statements ◦ Print a line a code after each step you ask the computer to do ◦ When it’s not printing or it prints something wrong, that’s where the mistake is ◦ Helps you see and find where your program stops working
56. Using Comments • You use comments to organize your code • Take notes • # ◦ Anything after the # will be turned into a comment ◦ That means it computer ignores and doesn’t read what is commented out in your code ◦ you can read it in the code, the computer can’t
57. Modifying Elements in a List 1. Create your list first 2. Find the index of the element that you want to change 3. Replace the element 4. print
58. Adding Elements to a List • Make your list • list_name.append(“…”) • Adds it to the end of the list • Make your list • list_name.insert(index#, “…”) • Adds it to the specified index
59. Removing Elements in a List • If you know the position of the item you want to remove: • del list_name[index#] • Or list_name.pop(index#) • If you want to remove the last item (sometimes you don’t know how long a list is) • List_name.pop() What do you get? To store it: motorcycles = motorcycles.pop() print(motorcycles)
60. When to use .pop() or del • When you want to delete an item from a list and not use the item in any way, use the del statement • If you want to use an item as you remove it, use pop() ◦ You can store a popped item into a variable
61. Remove item by value • Sometimes you don’t know the position of the value you want to remove • list_name.remove(‘nameofthingtoberemoved) • Everyone make a list of names, but include the name Bob in the list • Remove Bob’s name using the remove function
62. Maps
63. Maps • Is a collection of things (like a list or tuples) • Map has a key and a corresponding value ◦ One key works with one lock ◦ Same thing for maps ◦ You use a key to get through the lock / You use a key to get to the value
64. List Map • Uses brackets [ ] • Colons • Uses a colon to separate the key and the value • Uses braces { } • Colons to separate each key from its value
65. Activity • Make a map of people’s favorite sports • Find out Ethel Smyth’s favorite sports By accessing the map and using her name As the key print(map_name[‘Ethel Smyth’])
66. Extra • You can del and replace a value in a map the same way as list, but use the key deleting replacing
67. If and Else Statments
68. Yes or no? • In programming we ask a lot of yes or no questions • For example, we can ask, are you older than 20? ◦ If yes, respond with, “You are too old” ◦ If no, respond with, “You are young!”
69. Conditions • Those times of yes or no questions are called conditions • Or more popularly called if statements ◦ If, yes, then this, if no then that
70. Conditions • You can combine multiple questions and different responses • You can have more then one if statements
71. Try it out!
72. Block of Code • A block of code is a grouped set of programming statements This is a block of code
73. indentation • Indentation is important and has meaning • You group them together if they are related Change the indentation, you’re creating new blocks.
75. Error • You’ll get a syntax error
76. Conditions to Compare things • Comparing things in conditions • True (yes) False (no) • Or use operators to create conditions
78. Multiple conditions using else print(“Want to hear a dirty joke?”) age = 12 if age == 12 print(“A pig fell in the mud!”) else: print(“Shh It’s a secret.”) You can change the age To get a different message
79. If and Elif Statements • Elif is short for else-if • After reading this, what would be printed out?
80. Combining Conditions • You can combine conditions by using the keywords and & or
81. Combining conditions cont. if age >= 10 and age <= 13: print(‘What is 13+43+4353+5635+? A headache!’) else: print(‘Huh?’)
82. Special cases • You can assign variables with no value • None variable = None print(variable) None Then you should be able to do this, variable == None: print(“there’s nothing here”) The variable does not have a value
83. Reminder • String and numbers are very different • 10 is not equal to ‘10’ Remember when we converted an integer into a string? str(10)
84. Changing a string into an int • age = ‘10’ • convert_age = int(age)