Beyond Blocks: Python Session #1

Transcription

1 Beyond Blocks: Session #1 CS10 Spring 2013 Thursday, April 30, 2013 Michael Ball Beyond Blocks : : Session #1 by Michael Ball adapted from Glenn Sugden is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License. 1 1

2 Goals Quick introduction to Not a tutorial or how to Hope is that you ll want to learn (more) Advantages over higher level languages Challenges of programming syntax It s really like writing BYOB on Paper! 2 2

3 Beyond Blocks: #1 Installation: Mac Check Open Terminal Type python3 and hit return Type print( hello world ) and hit return The result should be: 3 3

4 Beyond Blocks: #1 Installation: Windows Check Get to "print" something with these instructions: (You only have to get to the "Many people use the interactive mode as a convenient yet highly programmable calculator" paragraph) 4 4

5 Beyond Blocks: #1 Installation: More Information Computer Science Circles : Run at Home cemclinux1.math.uwaterloo.ca/~cscircles/ wordpress/run-at-home/ 5 5

6 Beyond Blocks: #1 Installation: Version Check Michael> python3 -V We ll be talking about version 3.3.x here, although version 2.7.x (which is more common) works just as well! If curious, there s more version info at: 6 6

7 Beyond Blocks: #1 Why used text based programming? <demo> 7 7

8 8 8

9 Variables 9 9

10 Variables 10 10

11 Variables NOTE: Assignment doesn t evaluate to anything, so nothing is printed! 11 11

12 Variables 12 12

13 Variables print(var) NOTE: Printing is one of the big differences between 2 and 3. 3 requires () with print! For the sake of humanity, just use print()! :) 13 13

14 Operators 14 14

15 Types Everything in has an internal type Types are determined dynamically x = 1 x now has the type int : (short for integer ) We ll talk about this script (or function) later

16 Types: bool bool is short for boolean bool s can have two values: True False 16 16

17 Types: bool bool is short for boolean bool s can have two values: >>> type(true) <class 'bool'> True False >>> True True >>> False False NOTE: Upper case is important! 17 17

18 Types: function type() This function returns the type that has assigned the identifier. >>> type(true) <class 'bool'> >>> type(1) <class 'int'> >>> type(1.0) <class 'float'> >>> type("hello, there!") <class 'str'> >>> type("1") <class 'str'> 18 18

19 Operators 19 19

20 Operators 20 20

21 Operators Note the double =s! = means assign, == means compare Very common source of bugs! 21 21

22 Operators = means assign, == means compare 22 22

23 Operators = means assign, == means compare 23 23

24 Operators 24 24

25 Sidebar: Division (integer vs. real/float) 2 3 >>> 5/6 0 >>> 5.0/ >>> 5.0// >>> 5/ >>> 5.0/ >>> 5.0//

26 Sidebar: Division (integer vs. real/float) >>> 5/ >>> 5.0/ >>> 5.0// Force integer division 26

27 Sidebar: Exponent BYOB has e x and 10 x, but can do any base & exponent! >>> 2**8 256 >>> 2** >>> 2**

28 Conditionals 28 28

29 Conditionals 29

30 Conditionals Notice the colon and indentation syntax! 30

31 Conditionals Notice the colon and indentation syntax! 31

32 Conditionals 32 32

33 Conditionals 33

34 Loops 34 34

35 Loops 35

36 Loops Note the indentation (again)! 36

37 Loops 37 37

38 Loops 38

39 More Loops 39 39

40 Moar [sic] Loops There isn t really an exact equivalent of this in... We ll talk more about this in Session #

41 Functions: Calling Calling functions (the syntax) looks like this: Equivalent to creating & running a BYOB block: 41 41

42 Functions: Calling Calling functions (the syntax) looks like this: Equivalent to creating & running a BYOB block: 42

43 Functions: Calling Calling functions (the syntax) looks like this: Equivalent to creating & running a BYOB block: 43

44 Functions: Calling Calling functions (the syntax) looks like this: Equivalent to creating & running a BYOB block: 44

45 Functions : Defining Keyword: DEF 45 45

46 Functions : Defining Name of the function 46 46

47 Functions : Defining Arguments, or inputs to the function 47 47

48 Functions : Defining Indentation: the key to and scope.! In : Indentation matters!! 48 We ll talk about scope later... 48

49 Functions : Defining pass: s placeholder Skip this, and do nothing

50 Functions : Defining pass: s placeholder Skip this, and do nothing. Functions must have a body! 49 49

51 Functions : Defining 50

52 Functions : Defining Hitting Return/Enter (on an empty line) closes (finishes) the definition

53 Sidebar: Keywords Words reserved by and del from not while as elif global or with assert else if pass yield break except import class exec in raise continue finally is return def for lambda try List at: docs.python.org/reference/lexical_analysis.html 52 52

54 Built In Functions abs() dict() help() min() setattr() all() dir() hex() next() slice() any() divmod() id() object() sorted() ascii() enumerate() input() oct() staticmethod() bin() eval() int() open() str() bool() exec() isinstance() ord() sum() bytearray() filter() issubclass() pow() super() bytes() float() iter() print() tuple() callable() format() len() property() type() chr() frozenset() list() range() vars() classmethod() getattr() locals() repr() zip() compile() globals() map() reversed() import () complex() hasattr() max() round() delattr() hash() memoryview() set() 53 53

55 USEFUL: Built In Functions abs() help() min() max() print() range() type() str() chr() ord() bool() float() int() map() filter() sum() open() iter() len() tuple() list() dict() set()

56 Functions : Returning Values 55 55

57 Functions : Returning Values 56

58 Functions : Returning Values return and report are equivalent! 57

59 Functions : Recursion! 58 58

60 Functions : Recursion! 59 59

61 Functions : Recursion! Within Reason! 60

62 Beyond Blocks: #1 More Information.org: Docs: Modules: docs.python.org/modindex.html CodeAcademy: codeacademy.com Online Tutor:

63 Beyond Blocks: #1 More Information Computer Science Circles: cemclinux1.math.uwaterloo.ca/~cscircles/ wordpress/using-this-website/ Dive Into : diveintopython.org/toc/ Cal s Self-Paced Center: inst.eecs.berkeley.edu/~selfpace/class/cs9h/ How to Think Like a Computer Scientist ( Version)