1. An Introduction to Python Blake Brogdon

2. What is Python?  Python is an interpreted, interactive, object-oriented programming language. (from python.org)  Portable  Dynamic (type/language features)  GPL-compatible  Java-like or Pythonic code

3. History  Written by Guido van Rossum –CWI (Netherlands)  1991 –Released to USENET  1995 –Corporation for National Research Initiatives (Reston, VA)  2000 –BeOpen PythonLabs formed –Moved to Digital Creations (Zope Labs)  2001 –PSF formed  Non-profit organization created specifically to own Python-related Intellectual Property (python.org)

4. The Interactive Environment  Unlike Java, Python can be run in an interactive shell –Statements can be evaluated on the fly  Methods do not need to be a part of a class  A module is a file that contains Python code –Function, Class or even just expressions  To use a module’s code call “import modname” –ex. import os  To access that module’s members, prepend the module’s name to the member –ex. print os.path

5. Basic Syntax  Indentation replaces brackets  No semicolons  Files can be called anything  Unlike Java, Python uses colons  http://www.hetland.org/python/instant-python.php http://www.hetland.org/python/instant-python.php  Built-ins: –True, False, None (null)  Everything is an object –Even functions and classnames

6. Lists  Lists –Like Java’s arrays –Ex  [1,2,3]  [“Todd”, [“Blake”, “Pat”]] (lists can be nested)  [“Blake”, 3] (can mix types in lists) –Slicing  Like indexing…but better  Leads to very un-Java-like constructs

7. Dictionaries  Like Java/AP’s Hashtable class  Examples –{“a”:1, “b”:2, “c”:3} –{1:2, 3:4, 5:6}  Any combination of different types/lists

8. Functions  No access specifier(public/private)  No return type declaration  No typing of arguments  No brackets

9. Classes  No access specifier (private/public)  Constructor = __init__  All class methods take an implicit argument: self –Ex: __init__(self) –self == this  Instantiation does not require a “new”  Inheritance –class Dog(Animal): –Call to super via explicit superclass init call  Animal.__init__(self)  Instance variable –Set with self.myVar = 1 –Access with self.myVar

10. Interesting Features  Optional arguments  List comprehensions  Generators  “and”/“or” tricks  Lambda functions

11. List Comprehensions  Replace multi-line loops with a single statement  Output: [0, 2, 4, 6, 8]  range(x) returns all the numbers from 0 to x vs.

12. Generators  Functions that can return a value and maintain their state between calls  Yield vs. Return  Output: 0 1 2 3 4 5 6 7 8 9 10

13. Optional Arguments  Keyword arguments –A value is not necessary –Use value supplied at function definition –Like Java’s overloaded methods –Flexibility  Output: 0 1 2 3 4 5 6 7 8 9 10

14. “And”/“Or” Tricks  “Empty” values evaluate to false –ex: 0, False, None, [], ()  (Most) Everything else is True  A and B –If A is True return it. –If A is False return b  A or B –If a is true, then return it. –If it isn't, then return b.

15. Lambda Functions  An anonymous function –So you don’t have to declare a separate, small function  Must be an expression (no ‘print’)  Can have any number of args  Output: [1, 4, 9, 16, 25]  Note: –map(f, list) applies function f to each element in list –x**2 = x*x

16. How to Learn More  help(m) prints help for m –M can be a function, module, class or variable  dir(m) returns a list of all the public members of a module  obj.__doc__ is the documentation of a module, function or class  Links –http://rgruet.free.fr/PQR24/PQR2.4.htmlhttp://rgruet.free.fr/PQR24/PQR2.4.html –http://hetland.org/python/instant-pythonhttp://hetland.org/python/instant-python –http://python.org/doc/2.4/tut/tut.htmlhttp://python.org/doc/2.4/tut/tut.html –http://python.org/download/http://python.org/download/

17. Case Study  Documentation printer for all of the functions within a module