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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.

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Python Modules

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  1. Python Modules

  2. 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

  3. An example of a module • $ vim modex.py • def cube(x): • //Returns the value of x^3 • return x*x*x,

  4. Importing Modules • >>> import modex • >>> modex.cube(6) • 216 • >>> y = modex.cube(6) • >>>y • 216

  5. 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.

  6. From/import statements • Used to import specific functions from a module • >>> from modex import cube • >>> cube(3) • >>>27

  7. Executing modules as scripts • Python modules can be executed in command line whith • python modex.py <arguments>

  8. 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

  9. 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’]

  10. 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

  11. 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.

  12. Example of a package • math/ • __init__.py • triArea.py • sqArea.py • statistics/ • __init__.py • meanVal.py

  13. Example of using packages • >>> import math.sqArea • >>> math.sqArea.area(5) • 25 • >>> from math.sqArea import area • >>> area(5) • 25

  14. Questions?

  15. Sources • http://docs.python.org/tutorial/modules.html

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