__init__.py
specifies that the folder is actually a package. a package in python is a directory containing .py files (modules). In every folder which is a package (that is, a folder containing multiple .py files) you should define __init__.py
.
It can be empty, or you can put some statements to execute when the package is imported (or modules from the package).
For exmaple, let's take this directory tree:
/dev/package/greeter.py
and current working directory is /dev.
>>> from package import greeter
Traceback (most recent call last):
File "<pyshell#4>", line 1, in <module>
from package import greeter
ImportError: No module named package
import pakcage
results in the same error. When adding __init__.py into the package folder, it works. My init is simple as
print 'init executed'
>>> from package import greeter
init executed
>>>
One common functionality to put in __init__.py
is the __all__
variable. You can read more about it here Can someone explain __all__ in Python?