在 Python 中，用包来组织模块。

Python 包

两种类型的包：

1. 常规包
2. 命名空间包

常规包

常规包是包含 __init__.py 文件的目录。此文件指示应将目录视为包。__init__.py 文件可以为空，但它通常用于初始化包、定义向外部公开的内容或在导入包时运行设置代码。

mypackage/
    __init__.py
    module1.py
    module2.py

命名空间包

命名空间包是一种类似包的结构，不需要 __init__.py 文件，并且可以跨越多个目录。它允许分布式和灵活的包创建，从而可以将包的不同部分拆分到不同的位置。

例：

想象一下分布在两个目录中的命名空间包 mynamespace：

目录 1：

project1/mynamespace/
    module1.py

目录 2：

project2/mynamespace/
    module2.py

用法

import mynamespace.module1
import mynamespace.module2

Python 会将两个 mynamespace 目录合并到一个命名空间包中，使所有模块都可以访问。

比较

命名空间包示例

我们了解到 Namespace 包的源代码可以分布在多个目录中。它有助于根据团队对大型项目进行解耦，以便可以独立开发和分发包的组件。

例如：一个存储库（一个团队）可以处理一个组件，另一个团队可以处理同一包的另一个组件，但独立开发和分发。

让我们了解 Namespace 包如何帮助独立开发和分发包。

假设我们有一个公司 （log-corp） 提供了一个大而有用的包。但是该包的子包/模块在不同的存储库（目录）中是多样化的，因为不同的团队正在处理它。

• log_corp 是主包，其中包含许多跨团队开发并独立分发的子包和模块。
• 版本控制和包分发将独立进行。
• 他们唯一共享的是命名空间。（所有子包和模块都将归入主包log_corp）

团队 1（存储库 1）

使用 src 布局。

LOG_CORP_COMP1/
├── src/
│   └── log_corp/
│       ├── sub_pkg1/
│       │   └── sub_module1.py
│       └── module1.py
├── pyproject.toml
└── README.md

module1.py

def func1():
    print('From log-corp module1')

sub_module1.py

def sub_func1():
    print('From log-corp submodule1')

pyproject.toml 文件

[build-system]
requires = ["setuptools"]
build-backend = "setuptools.build_meta"

[project]
name = "log-corp1"  # as if it appears in pypi
authors = [
    {name = "Logesh", email = "log@gmail.com"},
]
description = "My package description"
readme = "README.md"
requires-python = ">=3.10"
license = {text = "MIT License"}
classifiers = [
    "Programming Language :: Python :: 3",
]
version = "1.0.1"   # version 1.0.1

构建软件包

PS C:\Users\L\Desktop\log_corp_comp1> ls


    Directory: C:\Users\L\Desktop\log_corp_comp1


Mode                 LastWriteTime         Length Name
----                 -------------         ------ ----
d-----        12/28/2024  11:32 AM                src
-a----        12/28/2024  11:41 AM            387 pyproject.toml
-a----        12/28/2024  11:31 AM             34 README.md


PS C:\Users\L\Desktop\log_corp_comp1> python -m build
* Creating isolated environment: venv+pip...
* Installing packages in isolated environment:
  - setuptools
* Getting build dependencies for sdist...
running egg_info
creating src\log_corp1.egg-info
writing src\log_corp1.egg-info\PKG-INFO
writing dependency_links to src\log_corp1.egg-info\dependency_links.txt
writing top-level names to src\log_corp1.egg-info\top_level.txt
writing manifest file 'src\log_corp1.egg-info\SOURCES.txt'
reading manifest file 'src\log_corp1.egg-info\SOURCES.txt'
writing manifest file 'src\log_corp1.egg-info\SOURCES.txt'
* Building sdist...
running sdist
running egg_info
writing src\log_corp1.egg-info\PKG-INFO
writing dependency_links to src\log_corp1.egg-info\dependency_links.txt
writing top-level names to src\log_corp1.egg-info\top_level.txt
reading manifest file 'src\log_corp1.egg-info\SOURCES.txt'
writing manifest file 'src\log_corp1.egg-info\SOURCES.txt'
running check
creating log_corp1-1.0.1
creating log_corp1-1.0.1\src\log_corp
creating log_corp1-1.0.1\src\log_corp1.egg-info
creating log_corp1-1.0.1\src\log_corp\sub_pkg1
copying files to log_corp1-1.0.1...
copying README.md -> log_corp1-1.0.1
copying pyproject.toml -> log_corp1-1.0.1
copying src\log_corp\module1.py -> log_corp1-1.0.1\src\log_corp
copying src\log_corp1.egg-info\PKG-INFO -> log_corp1-1.0.1\src\log_corp1.egg-info
copying src\log_corp1.egg-info\SOURCES.txt -> log_corp1-1.0.1\src\log_corp1.egg-info
copying src\log_corp1.egg-info\dependency_links.txt -> log_corp1-1.0.1\src\log_corp1.egg-info
copying src\log_corp1.egg-info\top_level.txt -> log_corp1-1.0.1\src\log_corp1.egg-info
copying src\log_corp\sub_pkg1\sub_module1.py -> log_corp1-1.0.1\src\log_corp\sub_pkg1
copying src\log_corp1.egg-info\SOURCES.txt -> log_corp1-1.0.1\src\log_corp1.egg-info
Writing log_corp1-1.0.1\setup.cfg
Creating tar archive
removing 'log_corp1-1.0.1' (and everything under it)
* Building wheel from sdist
* Creating isolated environment: venv+pip...
* Installing packages in isolated environment:
  - setuptools
* Getting build dependencies for wheel...
running egg_info
writing src\log_corp1.egg-info\PKG-INFO
writing dependency_links to src\log_corp1.egg-info\dependency_links.txt
writing top-level names to src\log_corp1.egg-info\top_level.txt
reading manifest file 'src\log_corp1.egg-info\SOURCES.txt'
writing manifest file 'src\log_corp1.egg-info\SOURCES.txt'
* Building wheel...
running bdist_wheel
running build
running build_py
creating build\lib\log_corp
copying src\log_corp\module1.py -> build\lib\log_corp
creating build\lib\log_corp\sub_pkg1
copying src\log_corp\sub_pkg1\sub_module1.py -> build\lib\log_corp\sub_pkg1
running egg_info
writing src\log_corp1.egg-info\PKG-INFO
writing dependency_links to src\log_corp1.egg-info\dependency_links.txt
writing top-level names to src\log_corp1.egg-info\top_level.txt
reading manifest file 'src\log_corp1.egg-info\SOURCES.txt'
writing manifest file 'src\log_corp1.egg-info\SOURCES.txt'
installing to build\bdist.win-amd64\wheel
running install
running install_lib
creating build\bdist.win-amd64\wheel
creating build\bdist.win-amd64\wheel\log_corp
copying build\lib\log_corp\module1.py -> build\bdist.win-amd64\wheel\.\log_corp
creating build\bdist.win-amd64\wheel\log_corp\sub_pkg1
copying build\lib\log_corp\sub_pkg1\sub_module1.py -> build\bdist.win-amd64\wheel\.\log_corp\sub_pkg1
running install_egg_info
Copying src\log_corp1.egg-info to build\bdist.win-amd64\wheel\.\log_corp1-1.0.1-py3.11.egg-info
running install_scripts
creating build\bdist.win-amd64\wheel\log_corp1-1.0.1.dist-info\WHEEL
creating 'C:\Users\L\Desktop\log_corp_comp1\dist\.tmp-ryh5ya6f\log_corp1-1.0.1-py3-none-any.whl' and adding 'build\bdist.win-amd64\wheel' to it
adding 'log_corp/module1.py'
adding 'log_corp/sub_pkg1/sub_module1.py'
adding 'log_corp1-1.0.1.dist-info/METADATA'
adding 'log_corp1-1.0.1.dist-info/WHEEL'
adding 'log_corp1-1.0.1.dist-info/top_level.txt'
adding 'log_corp1-1.0.1.dist-info/RECORD'
removing build\bdist.win-amd64\wheel
Successfully built log_corp1-1.0.1.tar.gz and log_corp1-1.0.1-py3-none-any.whl
PS C:\Users\L\Desktop\log_corp_comp1>

团队 2（存储库 2）

src 布局

LOG_CORP_COMP2/
├── src/
│   └── log_corp/
│       ├── sub_pkg2/
│       │   └── sub_module2.py
│       └── module2.py
├── pyproject.toml
└── README.md

module2.py

def func2():
    print('From log-corp module2')

sub_module2.py

def sub_func2():
    print('From log-corp submodule2')

pyproject.toml 文件

[build-system]
requires = ["setuptools"]
build-backend = "setuptools.build_meta"

[project]
name = "log-corp2"   # Different package name from the previous one
authors = [
    {name = "Logesh", email = "log@gmail.com"},
]
description = "My package description"
readme = "README.md"
requires-python = ">=3.10"
license = {text = "MIT License"}
classifiers = [
    "Programming Language :: Python :: 3",
]
version = "1.0.2"   # Different version 

构建了软件包

PS E:\Documents\log_corp_comp2> ls


    Directory: E:\Documents\log_corp_comp2


Mode                 LastWriteTime         Length Name
----                 -------------         ------ ----
d-----        12/28/2024  11:25 AM                src
-a----        12/28/2024  11:31 AM             34 README.md
-a----        12/28/2024  11:41 AM            387 pyproject.toml


PS E:\Documents\log_corp_comp2> python -m build
* Creating isolated environment: venv+pip...
* Installing packages in isolated environment:
  - setuptools
* Getting build dependencies for sdist...
running egg_info
creating src\log_corp2.egg-info
writing src\log_corp2.egg-info\PKG-INFO
writing dependency_links to src\log_corp2.egg-info\dependency_links.txt
writing top-level names to src\log_corp2.egg-info\top_level.txt
writing manifest file 'src\log_corp2.egg-info\SOURCES.txt'
reading manifest file 'src\log_corp2.egg-info\SOURCES.txt'
writing manifest file 'src\log_corp2.egg-info\SOURCES.txt'
* Building sdist...
running sdist
running egg_info
writing src\log_corp2.egg-info\PKG-INFO
writing dependency_links to src\log_corp2.egg-info\dependency_links.txt
writing top-level names to src\log_corp2.egg-info\top_level.txt
reading manifest file 'src\log_corp2.egg-info\SOURCES.txt'
writing manifest file 'src\log_corp2.egg-info\SOURCES.txt'
running check
creating log_corp2-1.0.2
creating log_corp2-1.0.2\src\log_corp
creating log_corp2-1.0.2\src\log_corp2.egg-info
creating log_corp2-1.0.2\src\log_corp\sub_pkg2
copying files to log_corp2-1.0.2...
copying README.md -> log_corp2-1.0.2
copying pyproject.toml -> log_corp2-1.0.2
copying src\log_corp\module2.py -> log_corp2-1.0.2\src\log_corp
copying src\log_corp2.egg-info\PKG-INFO -> log_corp2-1.0.2\src\log_corp2.egg-info
copying src\log_corp2.egg-info\SOURCES.txt -> log_corp2-1.0.2\src\log_corp2.egg-info
copying src\log_corp2.egg-info\dependency_links.txt -> log_corp2-1.0.2\src\log_corp2.egg-info
copying src\log_corp2.egg-info\top_level.txt -> log_corp2-1.0.2\src\log_corp2.egg-info
copying src\log_corp\sub_pkg2\sub_module2.py -> log_corp2-1.0.2\src\log_corp\sub_pkg2
Writing log_corp2-1.0.2\setup.cfg
Creating tar archive
removing 'log_corp2-1.0.2' (and everything under it)
* Building wheel from sdist
* Creating isolated environment: venv+pip...
* Installing packages in isolated environment:
  - setuptools
* Getting build dependencies for wheel...
running egg_info
writing src\log_corp2.egg-info\PKG-INFO
writing dependency_links to src\log_corp2.egg-info\dependency_links.txt
writing top-level names to src\log_corp2.egg-info\top_level.txt
reading manifest file 'src\log_corp2.egg-info\SOURCES.txt'
writing manifest file 'src\log_corp2.egg-info\SOURCES.txt'
* Building wheel...
running bdist_wheel
running build
running build_py
creating build\lib\log_corp
copying src\log_corp\module2.py -> build\lib\log_corp
creating build\lib\log_corp\sub_pkg2
copying src\log_corp\sub_pkg2\sub_module2.py -> build\lib\log_corp\sub_pkg2
running egg_info
writing src\log_corp2.egg-info\PKG-INFO
writing dependency_links to src\log_corp2.egg-info\dependency_links.txt
writing top-level names to src\log_corp2.egg-info\top_level.txt
reading manifest file 'src\log_corp2.egg-info\SOURCES.txt'
writing manifest file 'src\log_corp2.egg-info\SOURCES.txt'
installing to build\bdist.win-amd64\wheel
running install
running install_lib
creating build\bdist.win-amd64\wheel
creating build\bdist.win-amd64\wheel\log_corp
copying build\lib\log_corp\module2.py -> build\bdist.win-amd64\wheel\.\log_corp
creating build\bdist.win-amd64\wheel\log_corp\sub_pkg2
copying build\lib\log_corp\sub_pkg2\sub_module2.py -> build\bdist.win-amd64\wheel\.\log_corp\sub_pkg2
running install_egg_info
Copying src\log_corp2.egg-info to build\bdist.win-amd64\wheel\.\log_corp2-1.0.2-py3.11.egg-info
running install_scripts
creating build\bdist.win-amd64\wheel\log_corp2-1.0.2.dist-info\WHEEL
creating 'E:\Documents\log_corp_comp2\dist\.tmp-bn0t41tx\log_corp2-1.0.2-py3-none-any.whl' and adding 'build\bdist.win-amd64\wheel' to it
adding 'log_corp/module2.py'
adding 'log_corp/sub_pkg2/sub_module2.py'
adding 'log_corp2-1.0.2.dist-info/METADATA'
adding 'log_corp2-1.0.2.dist-info/WHEEL'
adding 'log_corp2-1.0.2.dist-info/top_level.txt'
adding 'log_corp2-1.0.2.dist-info/RECORD'
removing build\bdist.win-amd64\wheel
Successfully built log_corp2-1.0.2.tar.gz and log_corp2-1.0.2-py3-none-any.whl
PS E:\Documents\log_corp_comp2>

使用 log_corp

创建虚拟环境。

安装 log-corp 的一个组件

安装 log-corp 的另一个组件

因此，我们安装了 2 个共享相同命名空间的不同包（主包）。所以，现在这两个软件包 log_corp1 和 log_corp2 可以独立进行开发、分发、安装、升级、版本化。（仍然共享相同的命名空间，即所谓的 Namespace 包。

在这里，源的合并是在安装过程中自动完成的，并且在合并过程中没有冲突。这是使用 Namespace 包的主要好处之一。

将 log-corp 作为一个整体使用，它是从不同来源安装的。

一个明显的缺点是 import * 到 log_corp 无法按预期工作。

由于没有__init__.py文件来初始化包。

尝试使用常规软件包实现相同的效果

为两个组件添加 __init__.py，并在该文件中进行一些初始化。

组件 1

LOG_CORP_COMP1/
├── src/
│   └── log_corp/
│       ├── sub_pkg1/
│       │   ├── __init__.py
│       │   └── sub_module1.py
│       ├── __init__.py
│       └── module1.py
├── pyproject.toml
└── README.md

log_corp/__init__.py

from . import module1
from . import sub_pkg1

log_corp/sub_pkg1/__init__.py

from . import sub_module1

其余文件具有相同的内容。

组件 2

LOG_CORP_COMP2/
├── src/
│   └── log_corp/
│       ├── sub_pkg2/
│       │   ├── __init__.py
│       │   └── sub_module2.py
│       ├── __init__.py
│       └── module2.py
├── pyproject.toml
└── README.md

log_corp/__init__.py

from . import module2
from . import sub_pkg2

log_corp/sub_pkg2/__init__.py

from . import sub_module2

其余文件具有相同的内容。

构建两个软件包

组件 1

PS C:\Users\L\Desktop\log_corp_comp1> python -m build
* Creating isolated environment: venv+pip...
* Installing packages in isolated environment:
  - setuptools
* Getting build dependencies for sdist...
running egg_info
creating src\log_corp1.egg-info
<...truncated output>
removing build\bdist.win-amd64\wheel
Successfully built log_corp1-1.0.1.tar.gz and log_corp1-1.0.1-py3-none-any.whl
PS C:\Users\L\Desktop\log_corp_comp1>
PS C:\Users\L\Desktop\log_corp_comp1> ls


    Directory: C:\Users\L\Desktop\log_corp_comp1


Mode                 LastWriteTime         Length Name
----                 -------------         ------ ----
d-----        12/28/2024   1:31 PM                dist
d-----        12/28/2024   1:31 PM                src
-a----        12/28/2024  11:41 AM            387 pyproject.toml
-a----        12/28/2024  11:31 AM             34 README.md


PS C:\Users\L\Desktop\log_corp_comp1>

组件 2

PS E:\Documents\log_corp_comp2> python -m build
* Creating isolated environment: venv+pip...
* Installing packages in isolated environment:
  - setuptools
* Getting build dependencies for sdist...
running egg_info
creating src\log_corp2.egg-info
writing src\log_corp2.egg-info\PKG-INFO
writing dependency_links to src\log_corp2.egg-info\dependency_links.txt
writing top-level names to src\log_corp2.egg-info\top_level.txt
writing manifest file 'src\log_corp2.egg-info\SOURCES.txt'
reading manifest file 'src\log_corp2.egg-info\SOURCES.txt'
writing manifest file 'src\log_corp2.egg-info\SOURCES.txt'
* Building sdist...
running sdist
running egg_info
<...truncated output>
Writing log_corp2-1.0.2\setup.cfg
Creating tar archive
removing 'log_corp2-1.0.2' (and everything under it)
* Building wheel from sdist
* Creating isolated environment: venv+pip...
* Installing packages in isolated environment:
  - setuptools
* Getting build dependencies for wheel...
running egg_info
<...truncated output>
Successfully built log_corp2-1.0.2.tar.gz and log_corp2-1.0.2-py3-none-any.whl
PS E:\Documents\log_corp_comp2>

用法

已卸载之前安装的软件包。

安装软件包 log_corp1

在脚本中使用它。

module1 和 subpkg1 是可访问的

安装软件包 log_corp2

此安装会直接覆盖 log_corp/__init__.py 文件。

现在只有 log_corp2 的模块和子包可用。

但是我们仍然可以从 log_corp1 访问包/模块，将 log_corp 作为主包。

唯一需要注意的是，log_corp/__init__.py 被 log_corp2 覆盖。因此，如果我们有任何来自 log_corp1 的关键初始化将受到影响，这可能会导致包损坏问题。

结论

命名空间包是创建灵活且可扩展的 Python 包的现代方法。它们允许包的多个部分驻留在不同的目录中或分布在多个项目中。这使它们成为大型项目、插件系统或独立开发组件的情况的理想选择。

导入时的行为*

命名空间包不直接支持通配符导入（从 package import *），因为它们缺少 __init__.py 文件，其中常规包通常定义__all__列表来控制导入的内容。

命名空间包的优点

1. 模块化：包的不同部分可以拆分到多个项目或目录中。
2. 可扩展性：非常适合带有插件或独立开发组件的大型系统。
3. 易于维护：支持对包的特定部分进行更新，而不会影响整个结构。
4. 无__init__.py要求：简化包的创建并避免不必要的样板文件。
5. 改进的协作：团队可以并行处理包的不同部分，每个团队都拥有自己的目录。

命名空间包的缺点

1. 无__init__.py功能：如果没有 __init__.py 文件，您将无法初始化包、定义默认导入或设置包级逻辑。
2. 通配符导入的复杂性：不支持 import *，在某些用例中可能会带来不便。
3. 运行时组合：解析完整的包结构在运行时进行，如果目录配置错误，可能会导致细微的问题。
4. 调试挑战：由于软件包的各个部分分布在多个位置，因此调试和跟踪问题可能会更加困难。

将命名空间包用于分布式模块化系统或框架。对于更简单的项目或需要与较旧的 Python 版本兼容时，请坚持使用常规包。