Download Python Modules

Python
Modules
What are Python modules?
 Files
with previously written code that can
be imported to the Python interpreter.
A
module contains its own public and
private variables to prevent interferences
with user defined ones.
 Modules
file have .py extension
An example of a module
$
vim modex.py
 def
cube(x):
 //Returns the value of x^3
 return
x*x*x,
Importing Modules
 >>>
import modex
 >>> modex.cube(6)
 216
 >>> y = modex.cube(6)
 >>>y
 216
Accessing global variables in
a module
 Using
 >>>
dot notation.
a = anymodule.globalvar
 Note
that a global variables will not affect
another module; i.e. modify module1.gvar
will not change the value of
module2.gvar.
From/import statements
 Used
to import specific functions from a
module
 >>>
from modex import cube
 >>> cube(3)
 >>>27
Executing modules as scripts
 Python
modules can be executed in
command line whith
 python
modex.py <arguments>
Compiled Python files
 When
importing modex.py, a modex.pyc
file is generated.
 It contains the bytecode from the last
time modex.py is imported.
 If there is no .pyc file exists, it is created
 For future imports, these .pyc files are used
to speed up the loading time, not the
execution time
The dir() function
 This
function returns a list of modules and
functions that have been imported
 >>>
dir()
 [‘_ _name_ _’, ‘_ _package_ _’]
 >>>import modex
 >>>dir()
 [‘_ _name_ _’, ‘_ _package_ _’,’_
_modex’]
Standard Modules
 Python
comes with a library of standard modules.
 These modules contains built-in operations that are
not actually part of Python’s core
 Some of them are only imported based on the OS.
For instance: winreg module is only provided on
Windows systems.
 An important Std module is sys. it is used to change
the search path for the module
 >>>
sys.path.append(‘/home/pnp29/cs265_spring_2011
Packages
 They
are organized collections of
modules.
 Modules are stored in directories
 Each directory contains a __init__.py file
which tells the Python interpreter that it is
a package directory.
Example of a package
 math/
 __init__.py
 triArea.py
 sqArea.py
 statistics/
 __init__.py
 meanVal.py
Example of using packages
 >>>
import math.sqArea
 >>> math.sqArea.area(5)
 25
 >>> from math.sqArea import area
 >>> area(5)
 25
Questions?
Sources
 http://docs.python.org/tutorial/modules.html