This document summarizes a Python course on object-oriented programming and modules. Session 2 covers organizing and reusing code through scripts, classes, modules, and packages. It discusses importing modules and packages, the module search path, and using Eclipse with Python projects and modules.

1. CLTL Python Course
Object Oriented Programming in Python
2nd session
May 1st 2013

2. Reminder session 1
● What is Object Oriented Programming
● Classes, objects, methods, properties...
● How to define classes, with methods and attributes
● How to create objects
● The __init__ method
● Basic inheritance

3. Session 2
● How organize and reuse our code
– Scripts
– Classes
– Modules
– Packages
● How to use eclipse with python
– Creating projects, modules
– Example

4. Python modules
● A module is a file containing python definition and
statements
● The name of the module is the name of the file without .py
– File: fibo.py Name module: fibo
● The module name is important --> to reuse the module
– Import statement
● Inside the module the name is stored in the variable
__name__
● A script is a module which defines a MAIN function:
– When you run a module (python fibo.py) --> the mod.
Name is set to __main__
if __name__ == '__main__':

5. Importing modules
● Module “ruben” (file ruben.py)
– 3 functions: say_hello(), add(a,b), say_bye()
● We want to reuse this module in other modules
– import ruben
● Imports everything in the module
● Access: ruben.say_hello() ruben.add(2,3)
– from ruben import *
● Imports everything in the module
● Access: say_hello() say_bye()
– from ruben import add
● Imports only what you specify (add)
● Access: add(4,5)

6. More on modules
● Function dir(module) --> gives you all the content of the mod
– Import ruben
– dir(ruben) --> [...,'say_hello', 'add', 'say_bye']
● Module search path: (where python looks when “import”)
1. Current directory
2. PYTHONPATH environment variable
3. Default location in your installation
● You can modify inside your script the variable sys.path (list)
to modify the PYTHONPATH
● Import sys
● Sys.path.append('C:/ruben/example/my_code)

7. Python Packages
● A way of structure and reuse modules
● Access through “dotted module names”
– modA.modB.modC --> submodule modC inside
submodule modB inside module modA
● At low level a python package is a folder with some
python modules and one file called __init__.py
– This __init__ is called when we import the
package to initialization

8. Example Python Package
● Package to handle different sound files and data

9. Example Python Package
● Package to handle different sound files and data
DIFFERENT WAYS OF IMPORTING / USING
Import sounds.effects.echo
--> sunfs.effects.echo.echofilter(....)
From sound.effects import echo
--> echo.echofilter(....)
From sound.effects.echo import echofilter
--> echofilter(...)
From sound.effects import *
--> depends on the __all__ defined in
sound.effects.__init__
__all__ = ['echo','surround']

10. Eclipse + PyDev