# 3. 在 Windows 上使用 Python

This document aims to give an overview of Windows-specific behaviour you should know about when using Python on Microsoft Windows.

Unlike most Unix systems and services, Windows does not include a system supported installation of Python. To make Python available, the CPython team has compiled Windows installers (MSI packages) with every release for many years. These installers are primarily intended to add a per-user installation of Python, with the core interpreter and library being used by a single user. The installer is also able to install for all users of a single machine, and a separate ZIP file is available for application-local distributions.

As specified in PEP 11, a Python release only supports a Windows platform while Microsoft considers the platform under extended support. This means that Python 3.8 supports Windows Vista and newer. If you require Windows XP support then please install Python 3.4.

Windows提供了许多不同的安装程序，每个安装程序都有一定的优点和缺点。

完整安装程序 内含所有组件，对于使用Python 进行任何类型项目的开发人员而言，它是最佳选择。

Microsoft Store包 是一个简单的Python 安装，适用于运行脚本和包，以及使用IDLE或其他开发环境。 它需要Windows 10，但可以安全地安装而不会破坏其他程序。 它还提供了许多方便的命令来启动Python及其工具。

nuget.org 安装包 是用于持续集成系统的轻量级安装。它可用于构建Python包或运行脚本，但不可更新且没有用户界面工具。

可嵌入的包 是Python的最小安装包，适合嵌入到更大的应用程序中。

## 3.1. 完整安装程序

### 3.1.1. 安装步骤

Four Python 3.8 installers are available for download - two each for the 32-bit and 64-bit versions of the interpreter. The web installer is a small initial download, and it will automatically download the required components as necessary. The offline installer includes the components necessary for a default installation and only requires an internet connection for optional features. See 當安裝時不下載 for other ways to avoid downloading during installation.

After starting the installer, one of two options may be selected:

如果你選擇「馬上安裝」：

- You will not need to be an administrator (unless a system update for the C Runtime Library is required or you install the Python Launcher for Windows for all users)

- Python will be installed into your user directory

- The Python Launcher for Windows will be installed according to the option at the bottom of the first page

- The standard library, test suite, launcher and pip will be installed

- 如果選擇，安裝目錄將被加入到你的 `PATH`

- 安裝捷徑將只能被目前使用者所看見

選擇「客製化安裝」將允許你選擇所需的項目進行安裝，安裝位置與其他選擇或安裝後的所需進行的動作。你將需要使用此選項「除錯特徵」或「二進位方式」進行安裝。

To perform an all-users installation, you should select "Customize installation". In this case:

- You may be required to provide administrative credentials or approval

- Python will be installed into the Program Files directory

- The Python Launcher for Windows will be installed into the Windows directory

- Optional features may be selected during installation

- The standard library can be pre-compiled to bytecode

- If selected, the install directory will be added to the system `PATH`

- 捷徑將被所有使用者所見

### 3.1.2. Removing the MAX_PATH Limitation

Windows historically has limited path lengths to 260 characters. This meant that paths longer than this would not resolve and errors would result.

In the latest versions of Windows, this limitation can be expanded to approximately 32,000 characters. Your administrator will need to activate the "Enable Win32 long paths" group policy, or set the registry value `HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\FileSystem@LongPathsEnabled` to `1`.

This allows the `open()` function, the `os` module and most other path functionality to accept and return paths longer than 260 characters when using strings. (Use of bytes as paths is deprecated on Windows, and this feature is not available when using bytes.)

After changing the above option, no further configuration is required.

3.6 版更變: Support for long paths was enabled in Python.

### 3.1.3. 安裝排除使用者介面

All of the options available in the installer UI can also be specified from the command line, allowing scripted installers to replicate an installation on many machines without user interaction. These options may also be set without suppressing the UI in order to change some of the defaults.

To completely hide the installer UI and install Python silently, pass the `/quiet` option. To skip past the user interaction but still display progress and errors, pass the `/passive` option. The `/uninstall` option may be passed to immediately begin removing Python - no prompt will be displayed.

All other options are passed as `name=value`, where the value is usually `0` to disable a feature, `1` to enable a feature, or a path. The full list of available options is shown below.

Name | 描述 | 預設
--- | --- | ---
InstallAllUsers | Perform a system-wide installation. | 0
TargetDir | 安裝目錄 | Selected based on InstallAllUsers
DefaultAllUsersTargetDir | The default installation directory for all-user installs | `%ProgramFiles%\Python X.Y` or `%ProgramFiles(x86)%\Python X.Y`
DefaultJustForMeTargetDir | 預設安裝目錄給 只有給我 安裝方式 | `%LocalAppData%\Programs\PythonXY` 或 `%LocalAppData%\Programs\PythonXY-32` 或 `%LocalAppData%\Programs\PythonXY-64`
DefaultCustomTargetDir | The default custom install directory displayed in the UI | (empty)
AssociateFiles | 當執行程序也被安裝時創造檔案關聯 | 1
CompileAll | 編譯所有 `.py` 檔案為 `.pyc`。 | 0
PrependPath | Add install and Scripts directories to `PATH` and `.PY` to `PATHEXT` | 0
Shortcuts | Create shortcuts for the interpreter, documentation and IDLE if installed. | 1
Include_doc | 安裝Python文件 | 1
Include_debug | Install debug binaries | 0
Include_dev | Install developer headers and libraries | 1
Include_exe | Install `python.exe` and related files | 1
Include_launcher | Install Python Launcher for Windows. | 1
InstallLauncherAllUsers | Installs Python Launcher for Windows for all users. | 1
Include_lib | Install standard library and extension modules | 1
Include_pip | Install bundled pip and setuptools | 1
Include_symbols | Install debugging symbols (*.pdb) | 0
Include_tcltk | Install Tcl/Tk support and IDLE | 1
Include_test | Install standard library test suite | 1
Include_tools | Install utility scripts | 1
LauncherOnly | Only installs the launcher. This will override most other options. | 0
SimpleInstall | Disable most install UI | 0
SimpleInstallDescription | A custom message to display when the simplified install UI is used. | (empty)

For example, to silently install a default, system-wide Python installation, you could use the following command (from an elevated command prompt):

    python-3.8.0.exe /quiet InstallAllUsers=1 PrependPath=1 Include_test=0

To allow users to easily install a personal copy of Python without the test suite, you could provide a shortcut with the following command. This will display a simplified initial page and disallow customization:

    python-3.8.0.exe InstallAllUsers=0 Include_launcher=0 Include_test=0
        SimpleInstall=1 SimpleInstallDescription="Just for me, no test suite."

(Note that omitting the launcher also omits file associations, and is only recommended for per-user installs when there is also a system-wide installation that included the launcher.)

The options listed above can also be provided in a file named `unattend.xml` alongside the executable. This file specifies a list of options and values. When a value is provided as an attribute, it will be converted to a number if possible. Values provided as element text are always left as strings. This example file sets the same options as the previous example:

    <Options>
        <Option Name="InstallAllUsers" Value="no" />
        <Option Name="Include_launcher" Value="0" />
        <Option Name="Include_test" Value="no" />
        <Option Name="SimpleInstall" Value="yes" />
        <Option Name="SimpleInstallDescription">Just for me, no test suite</Option>
    </Options>

### 3.1.4. 當安裝時不下載

As some features of Python are not included in the initial installer download, selecting those features may require an internet connection. To avoid this need, all possible components may be downloaded on-demand to create a complete layout that will no longer require an internet connection regardless of the selected features. Note that this download may be bigger than required, but where a large number of installations are going to be performed it is very useful to have a locally cached copy.

Execute the following command from Command Prompt to download all possible required files. Remember to substitute `python-3.8.0.exe` for the actual name of your installer, and to create layouts in their own directories to avoid collisions between files with the same name.

    python-3.8.0.exe /layout [optional target directory]

You may also specify the `/quiet` option to hide the progress display.

### 3.1.5. Modifying an install

Once Python has been installed, you can add or remove features through the Programs and Features tool that is part of Windows. Select the Python entry and choose "Uninstall/Change" to open the installer in maintenance mode.

"Modify" allows you to add or remove features by modifying the checkboxes - unchanged checkboxes will not install or remove anything. Some options cannot be changed in this mode, such as the install directory; to modify these, you will need to remove and then reinstall Python completely.

"Repair" will verify all the files that should be installed using the current settings and replace any that have been removed or modified.

"Uninstall" will remove Python entirely, with the exception of the Python Launcher for Windows, which has its own entry in Programs and Features.

## 3.2. Microsoft Store包

3.7.2 版新加入.

Microsoft Store包是一个易于安装的Python解释器，主要用于交互式使用，例如，学生。

要安装软件包，请确保您拥有最新的Windows 10更新，并在Microsoft Store应用程序中搜索 "Python 3.8" 。确保您选择的应用程序由Python Software Foundation发布并安装。

警告

Python将始终在Microsoft Store上免费提供。如果要求您付款，则表示您没有选择正确的包。

安装完成后，可以在开始菜单中找到它来启动 Python。或者可以在命令提示符或 PowerShell 会话中输入 `python` 来启动。此外可以输入 `pip` 或 `idle` 来使用 pip 和 IDLE。IDLE 也在开始菜单中。

All three commands are also available with version number suffixes, for example, as `python3.exe` and `python3.x.exe` as well as `python.exe` (where `3.x` is the specific version you want to launch, such as 3.8). Open "Manage App Execution Aliases" through Start to select which version of Python is associated with each command. It is recommended to make sure that `pip` and `idle` are consistent with whichever version of `python` is selected.

可以使用 `python -m venv` 创建虚拟环境并激活并正常使用。

如果你已经安装了另一个版本的Python并将它添加到你的 `PATH` 变量中，那么它将作为 `python.exe` 而不是来自Microsoft Store的那个。要访问新安装，请使用 `python3.exe` 或 `python3.x.exe` 。

要删除Python，请打开“设置”并使用“应用程序和功能”，或者在“开始”中找到Python，然后右键单击以选择“卸载”。卸载将删除该已安装Python程序中的所有软件包，但不会删除任何虚拟环境

### 3.2.1. 已知的问题

目前， `py.exe` 启动程序在从Microsoft Store安装时不能用于启动Python。

由于Microsoft Store应用程序的限制，Python脚本可能无法对共享位置（如 `TEMP` ）和注册表进行完全写入访问。相反，它将写入私人副本。如果脚本必须修改共享位置，则需要安装完整安装程序。

## 3.3. nuget.org 安装包

3.5.2 版新加入.

nuget.org是一个精简的Python环境，用于在没有全局安装Python的系统的持续集成和构建。虽然Nuget是“.NET的包管理器”，但是对于包含构建时工具的包来说，它也可以很好地工作。

访问 nuget.org 获取有关使用nuget的最新信息。下面的摘要对Python开发人员来说已经足够了。

`nuget.exe` 命令行工具可以直接从 `https://aka.ms/nugetclidl` 下载，例如，使用curl或PowerShell。使用该工具安装64位或32位最新版本的Python:

    nuget.exe install python -ExcludeVersion -OutputDirectory .
    nuget.exe install pythonx86 -ExcludeVersion -OutputDirectory .

要选择特定版本，请添加 `-Version 3.x.y` 。输出目录可以从 `.` 更改，包将安装到子目录中。默认情况下，子目录的名称与包的名称相同，如果没有 `-ExcludeVersion` 选项，则此名称将包含已安装的特定版本。子目录里面是一个包含Python安装的 `tools` 目录:

    # Without -ExcludeVersion
    > .\python.3.5.2\tools\python.exe -V
    Python 3.5.2

    # With -ExcludeVersion
    > .\python\tools\python.exe -V
    Python 3.5.2

通常，nuget包不可升级，应该平行安装较新版本并使用完整路径引用。或者，手动删除程序包目录并再次安装。如果在构建之间不保留文件，许多CI系统将自动执行此操作。

除了 `tools` 目录外，还有一个 `build\native` 目录。它包含一个MSBuild属性文件 `python.props` ，可以在C++项目中使用该文件来引用Python安装。包含这些设置将自动在生成中使用标头和导入库。

nuget.org上的包信息页是 www.nuget.org/packages/python 对于64位版本和 www.nuget.org/packages/pythonx86 表示32位版本。

## 3.4. 可嵌入的包

3.5 版新加入.

The embedded distribution is a ZIP file containing a minimal Python environment. It is intended for acting as part of another application, rather than being directly accessed by end-users.

When extracted, the embedded distribution is (almost) fully isolated from the user's system, including environment variables, system registry settings, and installed packages. The standard library is included as pre-compiled and optimized `.pyc` files in a ZIP, and `python3.dll`, `python37.dll`, `python.exe` and `pythonw.exe` are all provided. Tcl/tk (including all dependants, such as Idle), pip and the Python documentation are not included.

備註

The embedded distribution does not include the Microsoft C Runtime and it is the responsibility of the application installer to provide this. The runtime may have already been installed on a user's system previously or automatically via Windows Update, and can be detected by finding `ucrtbase.dll` in the system directory.

Third-party packages should be installed by the application installer alongside the embedded distribution. Using pip to manage dependencies as for a regular Python installation is not supported with this distribution, though with some care it may be possible to include and use pip for automatic updates. In general, third-party packages should be treated as part of the application ("vendoring") so that the developer can ensure compatibility with newer versions before providing updates to users.

The two recommended use cases for this distribution are described below.

### 3.4.1. Python Application

An application written in Python does not necessarily require users to be aware of that fact. The embedded distribution may be used in this case to include a private version of Python in an install package. Depending on how transparent it should be (or conversely, how professional it should appear), there are two options.

Using a specialized executable as a launcher requires some coding, but provides the most transparent experience for users. With a customized launcher, there are no obvious indications that the program is running on Python: icons can be customized, company and version information can be specified, and file associations behave properly. In most cases, a custom launcher should simply be able to call `Py_Main` with a hard-coded command line.

The simpler approach is to provide a batch file or generated shortcut that directly calls the `python.exe` or `pythonw.exe` with the required command-line arguments. In this case, the application will appear to be Python and not its actual name, and users may have trouble distinguishing it from other running Python processes or file associations.

With the latter approach, packages should be installed as directories alongside the Python executable to ensure they are available on the path. With the specialized launcher, packages can be located in other locations as there is an opportunity to specify the search path before launching the application.

### 3.4.2. 嵌入 Python

Applications written in native code often require some form of scripting language, and the embedded Python distribution can be used for this purpose. In general, the majority of the application is in native code, and some part will either invoke `python.exe` or directly use `python3.dll`. For either case, extracting the embedded distribution to a subdirectory of the application installation is sufficient to provide a loadable Python interpreter.

As with the application use, packages can be installed to any location as there is an opportunity to specify search paths before initializing the interpreter. Otherwise, there is no fundamental differences between using the embedded distribution and a regular installation.

## 3.5. Alternative bundles

Besides the standard CPython distribution, there are modified packages including additional functionality. The following is a list of popular versions and their key features:

ActivePython

  Installer with multi-platform compatibility, documentation, PyWin32

Anaconda

  Popular scientific modules (such as numpy, scipy and pandas) and the `conda` package manager.

Canopy

  A "comprehensive Python analysis environment" with editors and other development tools.

WinPython

  Windows-specific distribution with prebuilt scientific packages and tools for building packages.

Note that these packages may not include the latest versions of Python or other libraries, and are not maintained or supported by the core Python team.

## 3.6. 設定 Python

To run Python conveniently from a command prompt, you might consider changing some default environment variables in Windows. While the installer provides an option to configure the PATH and PATHEXT variables for you, this is only reliable for a single, system-wide installation. If you regularly use multiple versions of Python, consider using the Python Launcher for Windows.

### 3.6.1. Excursus: Setting environment variables

Windows allows environment variables to be configured permanently at both the User level and the System level, or temporarily in a command prompt.

To temporarily set environment variables, open Command Prompt and use the set command:

    C:\>set PATH=C:\Program Files\Python 3.8;%PATH%
    C:\>set PYTHONPATH=%PYTHONPATH%;C:\My_python_lib
    C:\>python

These changes will apply to any further commands executed in that console, and will be inherited by any applications started from the console.

Including the variable name within percent signs will expand to the existing value, allowing you to add your new value at either the start or the end. Modifying `PATH` by adding the directory containing python.exe to the start is a common way to ensure the correct version of Python is launched.

To permanently modify the default environment variables, click Start and search for 'edit environment variables', or open System properties, Advanced system settings and click the Environment Variables button. In this dialog, you can add or modify User and System variables. To change System variables, you need non-restricted access to your machine (i.e. Administrator rights).

備註

Windows will concatenate User variables after System variables, which may cause unexpected results when modifying `PATH`.

The `PYTHONPATH` variable is used by all versions of Python 2 and Python 3, so you should not permanently configure this variable unless it only includes code that is compatible with all of your installed Python versions.

也參考

https://www.microsoft.com/en-us/wdsi/help/folder-variables

  環境變數於 Windows NT

https://technet.microsoft.com/en-us/library/cc754250.aspx

  The SET command, for temporarily modifying environment variables

https://technet.microsoft.com/en-us/library/cc755104.aspx

  The SETX command, for permanently modifying environment variables

https://support.microsoft.com/en-us/help/310519/how-to-manage-environment-variables-in-windows-xp

  如何管理環境變數於 Windows XP

https://www.chem.gla.ac.uk/~louis/software/faq/q1.html

  設定環境變數－Louis J. Farrugia

### 3.6.2. Finding the Python executable

3.5 版更變.

Besides using the automatically created start menu entry for the Python interpreter, you might want to start Python in the command prompt. The installer has an option to set that up for you.

On the first page of the installer, an option labelled "Add Python to PATH" may be selected to have the installer add the install location into the `PATH`. The location of the `Scripts\` folder is also added. This allows you to type python to run the interpreter, and pip for the package installer. Thus, you can also execute your scripts with command line options, see Command line documentation.

If you don't enable this option at install time, you can always re-run the installer, select Modify, and enable it. Alternatively, you can manually modify the `PATH` using the directions in Excursus: Setting environment variables. You need to set your `PATH` environment variable to include the directory of your Python installation, delimited by a semicolon from other entries. An example variable could look like this (assuming the first two entries already existed):

    C:\WINDOWS\system32;C:\WINDOWS;C:\Program Files\Python 3.8

## 3.7. Python Launcher for Windows

3.3 版新加入.

The Python launcher for Windows is a utility which aids in locating and executing of different Python versions. It allows scripts (or the command-line) to indicate a preference for a specific Python version, and will locate and execute that version.

Unlike the `PATH` variable, the launcher will correctly select the most appropriate version of Python. It will prefer per-user installations over system-wide ones, and orders by language version rather than using the most recently installed version.

启动器最初是在 PEP 397 中指定的。

### 3.7.1. 開始

#### 3.7.1.1. From the command-line

3.6 版更變.

System-wide installations of Python 3.3 and later will put the launcher on your `PATH`. The launcher is compatible with all available versions of Python, so it does not matter which version is installed. To check that the launcher is available, execute the following command in Command Prompt:

    py

You should find that the latest version of Python you have installed is started - it can be exited as normal, and any additional command-line arguments specified will be sent directly to Python.

If you have multiple versions of Python installed (e.g., 2.7 and 3.8) you will have noticed that Python 3.8 was started - to launch Python 2.7, try the command:

    py -2.7

If you want the latest version of Python 2.x you have installed, try the command:

    py -2

You should find the latest version of Python 2.x starts.

If you see the following error, you do not have the launcher installed:

    'py' is not recognized as an internal or external command,
    operable program or batch file.

Per-user installations of Python do not add the launcher to `PATH` unless the option was selected on installation.

#### 3.7.1.2. 虛擬環境（Virtual environment）

3.5 版新加入.

If the launcher is run with no explicit Python version specification, and a virtual environment (created with the standard library `venv` module or the external `virtualenv` tool) active, the launcher will run the virtual environment's interpreter rather than the global one. To run the global interpreter, either deactivate the virtual environment, or explicitly specify the global Python version.

#### 3.7.1.3. From a script

Let's create a test Python script - create a file called `hello.py` with the following contents

    #! python
    import sys
    sys.stdout.write("hello from Python %s\n" % (sys.version,))

From the directory in which hello.py lives, execute the command:

    py hello.py

You should notice the version number of your latest Python 2.x installation is printed. Now try changing the first line to be:

    #! python3

Re-executing the command should now print the latest Python 3.x information. As with the above command-line examples, you can specify a more explicit version qualifier. Assuming you have Python 2.6 installed, try changing the first line to `#! python2.6` and you should find the 2.6 version information printed.

Note that unlike interactive use, a bare "python" will use the latest version of Python 2.x that you have installed. This is for backward compatibility and for compatibility with Unix, where the command `python` typically refers to Python 2.

#### 3.7.1.4. 從檔案關聯

The launcher should have been associated with Python files (i.e. `.py`, `.pyw`, `.pyc` files) when it was installed. This means that when you double-click on one of these files from Windows explorer the launcher will be used, and therefore you can use the same facilities described above to have the script specify the version which should be used.

The key benefit of this is that a single launcher can support multiple Python versions at the same time depending on the contents of the first line.

### 3.7.2. Shebang Lines

If the first line of a script file starts with `#!`, it is known as a "shebang" line. Linux and other Unix like operating systems have native support for such lines and they are commonly used on such systems to indicate how a script should be executed. This launcher allows the same facilities to be used with Python scripts on Windows and the examples above demonstrate their use.

To allow shebang lines in Python scripts to be portable between Unix and Windows, this launcher supports a number of 'virtual' commands to specify which interpreter to use. The supported virtual commands are:

- `/usr/bin/env python`

- `/usr/bin/python`

- /usr/local/bin/python`

- `python`

For example, if the first line of your script starts with

    #! /usr/bin/python

The default Python will be located and used. As many Python scripts written to work on Unix will already have this line, you should find these scripts can be used by the launcher without modification. If you are writing a new script on Windows which you hope will be useful on Unix, you should use one of the shebang lines starting with `/usr`.

任何上述虚拟命令都可以显式指定版本（可以仅为主要版本，也可以为主要版本加次要版本）作为后缀。 此外，可以通过在次要版本之后添加 “-32” 来请求 32 位版本。 例如 `/usr/bin/python2.7-32` 将请求使用 32 位 python 2.7。

3.7 版新加入: 从python启动程序3.7开始，可以通过“-64”后缀调用64位版本。此外，可以指定没有次要的主要和架构（即 `/usr/bin/python3-64` ）。

The `/usr/bin/env` form of shebang line has one further special property. Before looking for installed Python interpreters, this form will search the executable `PATH` for a Python executable. This corresponds to the behaviour of the Unix `env` program, which performs a `PATH` search.

### 3.7.3. Arguments in shebang lines

The shebang lines can also specify additional options to be passed to the Python interpreter. For example, if you have a shebang line:

    #! /usr/bin/python -v

Then Python will be started with the `-v` option

### 3.7.4. Customization

#### 3.7.4.1. Customization via INI files

启动程序将搜索两个.ini文件 - 在当前用户的 "application data" 目录中搜索 `py.ini` （即通过使用 `CSIDL_LOCAL_APPDATA` 调用Windows函数 `SHGetFolderPath` 返回的目录）以及与启动器位于同一目录中的 `py.ini` 。相同的.ini文件既用于启动器的“控制台”版本（即 py.exe），也用于“windows”版本（即pyw.exe）

“应用程序目录”中指定的自定义优先于可执行文件旁边.ini文件的自定义，因此对启动程序旁边的.ini文件不具有写访问权限的用户可以覆盖该全局.ini文件中的命令。

#### 3.7.4.2. Customizing default Python versions

In some cases, a version qualifier can be included in a command to dictate which version of Python will be used by the command. A version qualifier starts with a major version number and can optionally be followed by a period ('.') and a minor version specifier. Furthermore it is possible to specify if a 32 or 64 bit implementation shall be requested by adding "-32" or "-64".

For example, a shebang line of `#!python` has no version qualifier, while `#!python3` has a version qualifier which specifies only a major version.

如果在命令中找不到版本限定符，则可以设置环境变量 `PY_PYTHON` 以指定默认版本限定符。 如果未设置，则默认为 "3"。 该变量可以指定能通过命令行传递的任何值，比如 "3", "3.7", "3.7-32" 或 "3.7-64"。 （请注意 "-64" 选项仅适用于 Python 3.7 或更高版本中包含的启动器。）

If no minor version qualifiers are found, the environment variable `PY_PYTHON{major}` (where `{major}` is the current major version qualifier as determined above) can be set to specify the full version. If no such option is found, the launcher will enumerate the installed Python versions and use the latest minor release found for the major version, which is likely, although not guaranteed, to be the most recently installed version in that family.

在安装了相同（major.minor）Python版本的32位和64位的64位Windows上，64位版本将始终是首选。对于启动程序的32位和64位实现都是如此 -- 这对于启动程序32位和64位都是正确的 -- 如果可用，32位启动程序将倾向于执行指定版本的64位Python安装。这样就可以预测启动器的行为，只知道PC上安装了哪些版本，而不考虑它们的安装顺序（即，不知道32位或64位版本的Python和相应的启动器是否是最后安装）。如上所述，可以在版本说明符上使用可选的“-32”或“-64”后缀来更改此行为。

Examples:

- If no relevant options are set, the commands `python` and `python2` will use the latest Python 2.x version installed and the command `python3` will use the latest Python 3.x installed.

- The commands `python3.1` and `python2.7` will not consult any options at all as the versions are fully specified.

- If `PY_PYTHON=3`, the commands `python` and `python3` will both use the latest installed Python 3 version.

- If `PY_PYTHON=3.1-32`, the command `python` will use the 32-bit implementation of 3.1 whereas the command `python3` will use the latest installed Python (PY_PYTHON was not considered at all as a major version was specified.)

- If `PY_PYTHON=3` and `PY_PYTHON3=3.1`, the commands `python` and `python3` will both use specifically 3.1

In addition to environment variables, the same settings can be configured in the .INI file used by the launcher. The section in the INI file is called `[defaults]` and the key name will be the same as the environment variables without the leading `PY_` prefix (and note that the key names in the INI file are case insensitive.) The contents of an environment variable will override things specified in the INI file.

For example:

- Setting `PY_PYTHON=3.1` is equivalent to the INI file containing:

    [defaults]
    python=3.1

- Setting `PY_PYTHON=3` and `PY_PYTHON3=3.1` is equivalent to the INI file containing:

    [defaults]
    python=3
    python3=3.1

### 3.7.5. Diagnostics

If an environment variable `PYLAUNCH_DEBUG` is set (to any value), the launcher will print diagnostic information to stderr (i.e. to the console). While this information manages to be simultaneously verbose and terse, it should allow you to see what versions of Python were located, why a particular version was chosen and the exact command-line used to execute the target Python.

## 3.8. Finding modules

Python usually stores its library (and thereby your site-packages folder) in the installation directory. So, if you had installed Python to `C:\Python\`, the default library would reside in `C:\Python\Lib\` and third-party modules should be stored in `C:\Python\Lib\site-packages\`.

To completely override `sys.path`, create a `._pth` file with the same name as the DLL (`python37._pth`) or the executable (`python._pth`) and specify one line for each path to add to `sys.path`. The file based on the DLL name overrides the one based on the executable, which allows paths to be restricted for any program loading the runtime if desired.

When the file exists, all registry and environment variables are ignored, isolated mode is enabled, and `site` is not imported unless one line in the file specifies `import site`. Blank paths and lines starting with `#` are ignored. Each path may be absolute or relative to the location of the file. Import statements other than to `site` are not permitted, and arbitrary code cannot be specified.

Note that `.pth` files (without leading underscore) will be processed normally by the `site` module when `import site` has been specified.

When no `._pth` file is found, this is how `sys.path` is populated on Windows:

- An empty entry is added at the start, which corresponds to the current directory.

- If the environment variable `PYTHONPATH` exists, as described in Environment variables, its entries are added next. Note that on Windows, paths in this variable must be separated by semicolons, to distinguish them from the colon used in drive identifiers (`C:\` etc.).

- Additional "application paths" can be added in the registry as subkeys of `\SOFTWARE\Python\PythonCore{version}\PythonPath` under both the `HKEY_CURRENT_USER` and `HKEY_LOCAL_MACHINE` hives. Subkeys which have semicolon-delimited path strings as their default value will cause each path to be added to `sys.path`. (Note that all known installers only use HKLM, so HKCU is typically empty.)

- If the environment variable `PYTHONHOME` is set, it is assumed as "Python Home". Otherwise, the path of the main Python executable is used to locate a "landmark file" (either `Lib\os.py` or `pythonXY.zip`) to deduce the "Python Home". If a Python home is found, the relevant sub-directories added to `sys.path` (`Lib`, `plat-win`, etc) are based on that folder. Otherwise, the core Python path is constructed from the PythonPath stored in the registry.

- If the Python Home cannot be located, no `PYTHONPATH` is specified in the environment, and no registry entries can be found, a default path with relative entries is used (e.g. `.\Lib;.\plat-win`, etc).

If a `pyvenv.cfg` file is found alongside the main executable or in the directory one level above the executable, the following variations apply:

- If `home` is an absolute path and `PYTHONHOME` is not set, this path is used instead of the path to the main executable when deducing the home location.

最終這所有的結果為：

- When running `python.exe`, or any other .exe in the main Python directory (either an installed version, or directly from the PCbuild directory), the core path is deduced, and the core paths in the registry are ignored. Other "application paths" in the registry are always read.

- When Python is hosted in another .exe (different directory, embedded via COM, etc), the "Python Home" will not be deduced, so the core path from the registry is used. Other "application paths" in the registry are always read.

- If Python can't find its home and there are no registry value (frozen .exe, some very strange installation setup) you get a path with some default, but relative, paths.

For those who want to bundle Python into their application or distribution, the following advice will prevent conflicts with other installations:

- Include a `._pth` file alongside your executable containing the directories to include. This will ignore paths listed in the registry and environment variables, and also ignore `site` unless `import site` is listed.

- If you are loading `python3.dll` or `python37.dll` in your own executable, explicitly call `Py_SetPath()` or (at least) `Py_SetProgramName()` before `Py_Initialize()`.

- Clear and/or overwrite `PYTHONPATH` and set `PYTHONHOME` before launching `python.exe` from your application.

- If you cannot use the previous suggestions (for example, you are a distribution that allows people to run `python.exe` directly), ensure that the landmark file (`Lib\os.py`) exists in your install directory. (Note that it will not be detected inside a ZIP file, but a correctly named ZIP file will be detected instead.)

These will ensure that the files in a system-wide installation will not take precedence over the copy of the standard library bundled with your application. Otherwise, your users may experience problems using your application. Note that the first suggestion is the best, as the others may still be susceptible to non-standard paths in the registry and user site-packages.

> 3.6 版更變:

> - Adds `._pth` file support and removes `applocal` option from `pyvenv.cfg`.

> - Adds `pythonXX.zip` as a potential landmark when directly adjacent to the executable.

> 3.6 版後已棄用:

> Modules specified in the registry under `Modules` (not `PythonPath`) may be imported by `importlib.machinery.WindowsRegistryFinder`. This finder is enabled on Windows in 3.6.0 and earlier, but may need to be explicitly added to `sys.meta_path` in the future.

## 3.9. Additional modules

Even though Python aims to be portable among all platforms, there are features that are unique to Windows. A couple of modules, both in the standard library and external, and snippets exist to use these features.

The Windows-specific standard modules are documented in MS Windows Specific Services.

### 3.9.1. PyWin32

The PyWin32 module by Mark Hammond is a collection of modules for advanced Windows-specific support. This includes utilities for:

- 组件对象模型 (COM)

- Win32 API calls

- 登錄檔（Registry）

- 事件日誌（Event log）

- Microsoft Foundation Classes (MFC) user interfaces

PythonWin is a sample MFC application shipped with PyWin32. It is an embeddable IDE with a built-in debugger.

也參考

Win32 How Do I...?

  by Tim Golden

Python and COM

  by David and Paul Boddie

### 3.9.2. cx_Freeze

cx_Freeze is a `distutils` extension (see Extending Distutils) which wraps Python scripts into executable Windows programs (`*.exe` files). When you have done this, you can distribute your application without requiring your users to install Python.

### 3.9.3. WConio

Since Python's advanced terminal handling layer, `curses`, is restricted to Unix-like systems, there is a library exclusive to Windows as well: Windows Console I/O for Python.

WConio is a wrapper for Turbo-C's `CONIO.H`, used to create text user interfaces.

## 3.10. 編譯 Python 在 Windows

If you want to compile CPython yourself, first thing you should do is get the source. You can download either the latest release's source or just grab a fresh checkout.

The source tree contains a build solution and project files for Microsoft Visual Studio 2015, which is the compiler used to build the official Python releases. These files are in the `PCbuild` directory.

Check `PCbuild/readme.txt` for general information on the build process.

For extension modules, consult Building C and C++ Extensions on Windows.

也參考

Python + Windows + distutils + SWIG + gcc MinGW

  or "Creating Python extensions in C/C++ with SWIG and compiling them with MinGW gcc under Windows" or "Installing Python extension with distutils and without Microsoft Visual C++" by Sébastien Sauvage, 2003

MingW -- Python 扩展

## 3.11. 其他平台

With ongoing development of Python, some platforms that used to be supported earlier are no longer supported (due to the lack of users or developers). Check PEP 11 for details on all unsupported platforms.

- Windows CE is still supported.

- The Cygwin installer offers to install the Python interpreter as well (cf. Cygwin package source, Maintainer releases)

See Python for Windows for detailed information about platforms with pre-compiled installers.