Packages

Packages are a way to structure Python's module namespace. Essentially a package is just a collection of modules. A module named __**init.py\_ **_is required to treat the directory as a package. This file can contain initialization code... but it's often best to leave it blank.

Package Structure

math_stuff/ #top directory 
    __init__.py #special module 
    fib.py #fib module 
    triangle.py #triangle module 
    Calculator.py #calculator class module
more_math_stuff/ #additional package 
    __init__.py 
        other_modules.py

How to Import From a Package

So let's take the package below and walk through an import.

math_stuff/
    __init__.py
    fib.py
    triangle.py # run this file
    Calculator.py
    more_math_stuff/
        __init__.py 
        other_modules.py # import this module

from more_math_stuff import other_modules as om

om.do_something()

Useful Commands

• dir()

• • returns list of names in current local scope or with argument, attempts to return a list of valid attributes for object
• help()
• • Invokes built-in help system

# dir
>>> print dir()
['__builtins__', '__doc__', '__name__', '__package__']
>>> import(struct)
>>> print dir()
['__builtins__', '__doc__', '__name__', '__package__', 'struct']
>>> print dir(struct)
['Struct', '__builtins__', '__doc__', '__file__', '__name__', '__package__', '_clearcache', 'calcsize', 'error', 'pack', 'pack_into', 'unpack', 'unpack_from']

# help
print help(struct)
# Try it
print help()
# Try it