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Modules
As your programs grow in size, you'll probably want to break them into multiple files for easier maintenance. To do this, Python allows you to put definitions in a file and use them as a module that can be imported into other programs and scripts. To create a module, put the relevant statements and definitions into a file that has the same name as the module. (Note: The file must have a .py suffix.) For example:
# file : div.py def divide(a,b): q = a/b # If a and b are integers, q is an integer r = a - q*b return (q,r)
To use your module in other programs, you can use the import statement:
import div a, b = div.divide(2305, 29)
import creates a new namespace that contains all the objects defined in the module. To access this namespace, simply use the name of the module as a prefix, as in div.divide() in the preceding example.
If you want to import a module using a different name, supply the import statement with an optional as qualifier as follows:
import div as foo a,b = foo.divide(2305,29)
To import specific definitions into the current namespace, use the from statement:
from div import divide a,b = divide(2305,29) # No longer need the div prefix
To load all of a module's contents into the current namespace, you can also use the following:
from div import *
Finally, the dir() function lists the contents of a module and is a useful tool for interactive experimentation, since it can be used to provide a list of available functions and variables:
>>> import string >>> dir(string) ['__builtins__', '__doc__', '__file__', '__name__', '_idmap', '_idmapL', '_lower', '_swapcase', '_upper', 'atof', 'atof_error', 'atoi', 'atoi_error', 'atol', 'atol_error', 'capitalize', 'capwords', 'center', 'count', 'digits', 'expandtabs', 'find', ... >>>