What is __init__.py for?

python module package python-packaging
Mat picture Mat · Jan 15, 2009 · Viewed 1.3M times · Source

What is __init__.py for in a Python source directory?

Answer

Loki picture Loki · Jan 15, 2009

It used to be a required part of a package (old, pre-3.3 "regular package", not newer 3.3+ "namespace package").

Here's the documentation.

Python defines two types of packages, regular packages and namespace packages. Regular packages are traditional packages as they existed in Python 3.2 and earlier. A regular package is typically implemented as a directory containing an __init__.py file. When a regular package is imported, this __init__.py file is implicitly executed, and the objects it defines are bound to names in the package’s namespace. The __init__.py file can contain the same Python code that any other module can contain, and Python will add some additional attributes to the module when it is imported.

But just click the link, it contains an example, more information, and an explanation of namespace packages, the kind of packages without __init__.py.

Related questions

Python 3: ImportError "No Module named Setuptools"

I'm having troubles with installing packages in Python 3. I have always installed packages with setup.py install. But now, when I try to install the ansicolors package I get: importerror "No Module named Setuptools" I have no idea what to …

Read More
Can't import my own modules in Python

I'm having a hard time understanding how module importing works in Python (I've never done it in any other language before either). Let's say I have: myapp/__init__.py myapp/myapp/myapp.py myapp/myapp/SomeObject.py myapp/tests/TestCase.…

Read More
What's the difference between a Python module and a Python package?

What's the difference between a Python module and a Python package? See also: What's the difference between "package" and "module" (for other languages)

Read More