What Does Python’s __init__.py Do?

Python’s special __init__.py file marks a directory as a regular Python package and allows you to import its modules. This file runs automatically the first time you import its containing package. You can use it to initialize package-level variables, define functions or classes, and structure the package’s namespace clearly for users.

By the end of this video course, you’ll understand that:

• A directory without an __init__.py file becomes a namespace package, which behaves differently from a regular package and may cause slower imports.
• You can use __init__.py to explicitly define a package’s public API by importing specific modules or functions into the package namespace.
• The Python convention of using leading underscores helps indicate to users which objects are intended as non-public, although this convention can still be bypassed.
• Code inside __init__.py runs only once during the first import, even if you run the import statement multiple times.

Understanding how to effectively use __init__.py helps you structure your Python packages in a clear, maintainable way, improving usability and namespace management.

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