Is `__init__.py` Still Required for Python Packages in Version 3.3 ?

Python's __init__.py file is no longer a required element of the package in version 3.3

Question

Is it no longer required in Python 3.3? Provide __init__.py file for package?

Parsing

Introduction: The role of the __init__.py file

In Python, the role of the __init__.py file is to identify a directory as a package. Allows the different directories and modules of this directory to be organized into a namespace. In Python 2.7 and earlier, the __init__.py file is required to create a package.

__init__.py file in Python 3.3

In Python 3.3, the concept of implicit namespace packages was introduced, which makes it possible even without __init__.py Files and packages can also be created. This means that a directory can now be designated as a namespace package and the contents of that directory can be modularized.

Use cases for namespace packages

The most common use case for this implicit namespace package feature is to allow multiple libraries from different locations to contribute sub-packages to a parent package . For example, suppose there are two libraries google_pubsub and google_storage, which provide the following structure:

google_pubsub/              # 包 1
    google/                 # 命名空间包（没有 __init__.py）
        cloud/              # 命名空间包（没有 __init__.py）
            pubsub/         # 常规包（有 __init__.py）
                __init__.py # 必需的，用于创建常规包
                foo.py

google_storage/             # 包 2
    google/                 # 命名空间包（没有 __init__.py）
        cloud/              # 命名空间包（没有 __init__.py）
            storage/        # 常规包（有 __init__.py）
                __init__.py # 必需的，用于创建常规包
                bar.py

In this case, the google/ and google/cloud/ directories must be namespace packages, so that google_pubsub and The google_storage package is considered a sub-package under the same parent package.

Conclusion:

• There are the following two types of Python packages:

  • Namespace package (implicit package): No __init__.py file is required, used to contribute the contents of multiple libraries to a parent package.
  • Regular packages (explicit packages): Requires an __init__.py file to identify the package and only contains the contents of the current directory.
• For most cases it is still recommended to use regular packages (i.e. packages with __init__.py files) as they are simpler and easier to understand.
• The __init__.py file should not be used only in specific cases where namespace packages need to be created.

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