What are packages and how to create and use packages
Get to know packages
Packages are used to organize modules. While a module is stored in a file with the file name extension .py, a package is a directory.
To make Python treat it as a package,
the folder must contain a file (module) named __init__.py.
The contents of __init__.py is the contents of the package,
if you import it as if it were a plain module.
For example, if you have a package named constants, and the file constants/__init__.py contains the statement PI = 3.14, you would be able to do the following:
import constants
print constants.PI
The following table illustrates a simple package layout.
To put modules inside a package, we can put the module files inside the package directory. For example, if you wanted a package called drawing, which contained one module called shapes and one called colors, you would need the files and directories as the follows.
| File/Directory | Description |
|---|---|
| ~/python/ | Directory in PYTHONPATH |
| ~/python/drawing/ | Package directory (drawing package) |
| ~/python/drawing/__init__.py | Package code ("drawing module") |
| ~/python/drawing/colors.py | colors module |
| ~/python/drawing/shapes.py | shapes module |
| ~/python/drawing/gradient.py | gradient module |
| ~/python/drawing/text.py | text module |
| ~/python/drawing/image.py | image module |
With this setup, the following statements are all legal:
import drawing # (1) Imports the drawing package
import drawing.colors # (2) Imports the colors module
from drawing import shapes # (3) Imports the shapes module
After the first statement, import drawing,
the contents of the __init__ module in drawing would be
available but the drawing and colors modules would not be available.
After the second statement, import drawing.colors,
the colors module would be available,
but only under its full name, drawing.colors.
After the third statement from drawing import shapes,
the shapes module would be available, under its short name shapes.