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Python 101: Python for Absolute Beginners (PyTexas 2014)

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If you're absolutely new to Python, and to programming in general, this is the place to start!

Here's the breakdown: by the end of this workshop, you'll have Python downloaded onto your personal machine; have a general idea of what Python can help you do; be pointed in the direction of some excellent practice materials; and have a basic understanding of the syntax of the language.

Please don't forget to bring your laptop!

Audience: "Python 101" is geared toward individuals who are new to programming. If you've had some programming experience (shell scripting, MATLAB, Ruby, etc.), then you'll probably want to check out the more intermediate workshop, "Python 101++".

Published in: Technology

Python 101: Python for Absolute Beginners (PyTexas 2014)

  1. 1. Python 101: Python for Absolute Beginners PyTexas 2014
  2. 2. What is programming?
  3. 3. A computer is a machine that stores pieces of information. A computer also moves, arranges, and controls that information (or data). A program is a detailed set of instructions that tells a computer what to do with that data.
  4. 4. CodeSkulptor!
  5. 5. CodeSkulptor  Developed by Scott Rixner of Rice University to use for COMP 200.  Based on CodeMirror and Skulpt.  www.codeskulptor.org  If you want to learn more about using Python with CodeSkulptor after this class, check out the Coursera course “An Introduction to Interactive Programming in Python”! (9/15 – 11/16)  https://www.coursera.org/course/ interactivepython
  6. 6. Interacting with CodeSkulptor  Run  Save  Fresh URL  Open Local  Reset
  7. 7. Additional Resources  Docs (documentation)  Demos  Viz Mode
  8. 8. Let’s see what this thing can do…
  9. 9. Recap: Explore! Makes changes, see how they impact the program as a whole. When in doubt, check the documentation. When super in doubt, Google it.
  10. 10. Math
  11. 11. Math Try typing this into CodeSkuptor: >>> print 3 + 12 >>> print 12 - 3 >>> print 9 + 5 – 15 + 12 Operators: add: + subtract: - Note: don’t type the arrows >>> !
  12. 12. Math Rule: If you want Python to answer in floats, you have to talk to it in floats. More operators: divide: / multiply: * >>> print 3 * 12 >>> print 12 / 3 >>> print 11 // 3 >>> print 12.0 / 3.0 >>> print 11.0 / 3.0 >>> print 11.0 // 3.0
  13. 13. Math Comparison operators: == Equal to != Not equal to < Less than > Greater than <= Less than or equal to >= Greater than or equal to
  14. 14. Math Practice: >>> print 2 < 3 True >>> print 2 <= 2 False >>> print 3 > 2 True >>> print 2 != 3 True >>> print False < True True
  15. 15. Strings
  16. 16. Strings Examples: Try typing one without quotes: What’s the result? >>> “It’s a beautiful day!” >>> “Goodbye, cruel world.” >>> Aggies >>> “Aggies” >>> “Rice fight, never die!” >>> “3 + 2”
  17. 17. Strings String operators: concatenation: + multiplication: * Try concatenating: Try multiplying: >>> print “Hello” + “ “ + “world!” >>> print “HAHA” * 250
  18. 18. Variables
  19. 19. Variables Calculate a value: How can you save that value? Give the value a name: >>> print 21 + 21 42 >>> ultimate_answer = 42 >>> ultimate_answer 42
  20. 20. Variables Create a variable and give it a value: Now assign a new value: >>> headmaster = “Dumbledore” >>> print headmaster ‘Dumbledore’ >>> headmaster = “Hardcastle” >>> print headmaster ‘Hardcastle’ >>> color = “Brad Neely” >>> color = 12
  21. 21. Variables  You can calculate a variable once, but keep the result to use later.  You can keep the same name for a variable, but change the value. Some other things that we can do with variables: Get an index from a string: Do some math: >>> headmaster = “Dumbledore” >>> print headmaster[2] >>> number = 3 >>> print headmaster[number - 2]
  22. 22. Types of data
  23. 23. Data Types We already know about three types of data: “Whoop!” string 42 integer 3.14159 float Python can tell us about types using the type() function: >>> print type(“Whoop!”) <type ‘str’> How would we get Python to output int and float types?
  24. 24. Data Type: Lists
  25. 25. Lists List: a sequence of objects >>> Beatles = [“John”, “Paul”, “George”, “Ringo”] >>> grades = [82, 93, 67, 99, 100] Guess what this will output: >>> type(Beatles) >>> type(grades)
  26. 26. Lists List: a sequence of objects >>> Beatles = [“John”, “Paul”, “George”, “Ringo”] >>> grades = [82, 93, 67, 99, 100] Guess what this will output: >>> type(Beatles) <type ‘list’> >>> type(grades) <type ‘list’>
  27. 27. Lists Index: Where an item is in the list >>> Beatles = [“John”, “Paul”, “George”, “Ringo”] >>> Beatles[0] ‘John‘ [“John”, “Paul”, “George”, “Ringo”] 0 1 2 3 Python always starts at zero!
  28. 28. Data Type: Booleans
  29. 29. Booleans A boolean value can be: Is 1 equal to 1? Is 15 less than 5? True or False. >>> print 1 == 1 True >>> print 15 < 5 False
  30. 30. Booleans What happens when we type Boolean values in the interpreter? When the words ‘True’ and ‘False’ begin with upper case letters, Python knows to treat them like Booleans instead of strings or integers. >>> True >>> False >>> true >>> false >>> type(True) >>> type(“True”)
  31. 31. Booleans and If both comparisons are True: If only one of the comparisons is True: If both of the comparisons are False: >>> 1==1 and 2==2 True >>> 1==1 and 2==3 False >>> 1==2 and 2==3 False
  32. 32. Booleans or If both comparisons are True: If only one of the comparisons is True: If both of the comparisons are False: >>> 1==1 or 2==2 True >>> 1==1 or 2!=2 True >>> 1==2 or 2==3 False
  33. 33. Booleans not You can use the word not to reverse the answer that Python gives: Any expression that is True can become False: >>> 1==1 True >>> not 1==1 False >>> not True False
  34. 34. Booleans You can also use Booleans in their own expressions: >>> True and True >>> True and False >>> False and False >>> True or True >>> False or True >>> False or False >>> not True and True >>> not True or True
  35. 35. Logic
  36. 36. if Statements
  37. 37. if Statements Making decisions: If a condition is met, perform an action: “If you’re hungry, let’s eat lunch.” “If you like Frisbee, let’s play!” >>> state = “Texas” >>> if state == “Texas”: print “TX” TX
  38. 38. if Statements Adding a choice: Adding a choice in our code with the else clause: “If you’re hungry, let’s eat lunch. Or else we can eat in an hour.” “If you like Frisbee, let’s play! Or else we can play rugby.” >>> if state == “Texas” print “TX” else: print “[inferior state]”
  39. 39. if Statements Adding many choices: Adding more choices in our code with the elif clause: “If you like Frisbee, let’s play! Or else we can play rugby. Or else we can play Bioshock, or Half-Life, or Portal…” >>> if name == “Paige” print “Hi Paige!” elif name == “Walker”: print “Hi Walker!” else: print “Imposter!”
  40. 40. Loops
  41. 41. Loops Loops are chunks of code that repeat a task over and over again.  Counting loops repeat a certain number of times.  Conditional loops keep going until a certain thing happens (or as long as some condition is True).
  42. 42. Loops Counting loops repeat a certain number of times – they keep going until they get to the end of a count. >>> for mynum in [1, 2, 3, 4, 5]: print "Hello", mynum Hello 1 Hello 2 Hello 3 Hello 4 Hello 5 The for keyword is used to create this kind of loop, so it is usually just called a for loop.
  43. 43. Loops Conditional loops repeat until something happens (or as long as some condition is True). >>> count = 0 >>> while (count < 4): print 'The count is:', count count = count + 1 The count is: 0 The count is: 1 The count is: 2 The count is: 3 The while keyword is used to create this kind of loop, so it is usually just called a while loop.
  44. 44. Algorithms
  45. 45. Algorithms Really just means “set of instructions” Secret: computers aren’t very smart.
  46. 46. How would I make a pot of coffee? 1. Get a flavor of ground coffee. 2. Get a coffee maker. 3. Get filter paper. 4. Get a pot of water. 5. Make sure the coffee maker is plugged in… …and on, and on, and on. But to us, it’s just “make a pot of coffee”.
  47. 47. Functions
  48. 48. Remember how Algorithms are just instructions?  Functions are just a concise way to group instructions into a bundle. What it's like in our minds: “Make a pot of coffee.”  bundle In Python, you could say it like this: make_coffee(coffee_grounds, coffee_pot, water, filter_paper) ^ ^-----------------^---------------^-----------------^ function name function parameters
  49. 49. Functions Let’s define a function in CodeSkulptor: >>> def beverage(): print ‘Have you had a cup of coffee today?’ Now we’ll call the function: >>> beverage() Have you had a cup of coffee today?
  50. 50. Functions But what if not everyone wants a cup of coffee? Let’s define a function with parameters: >>> def beverage(drink): print “Have you had a cup of ” + drink + “ today?’ Now we’ll call the function: >>> beverage(“Monster Zero”) Have you had a cup of Monster Zero today?
  51. 51. Functions  Functions are defined using def.  Functions are called using parentheses ().  Functions take parameters and return outputs.  print displays information, but does not give a value.  return gives a value to the caller.
  52. 52. Thanks so much! Any questions?

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