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 3.9 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 3.9 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:

[圖片]

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\F
ileSystem@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 | "%ProgramFiles%\Python     |
|                             | all-user installs                      | X.Y" or "%ProgramFiles(x8  |
|                             |                                        | 6)%\Python X.Y"            |
+-----------------------------+----------------------------------------+----------------------------+
| DefaultJustForMeTargetDir   | 預設安裝目錄給 只有給我  安裝方式      | "%LocalAppData%\Programs\  |
|                             |                                        | PythonXY" 或 "%LocalAppDa  |
|                             |                                        | ta%\Programs\PythonXY-32"  |
|                             |                                        | 或 "%LocalAppData%\Progra  |
|                             |                                        | ms\PythonXY-64"            |
+-----------------------------+----------------------------------------+----------------------------+
| DefaultCustomTargetDir      | The default custom install directory   | (empty)                    |
|                             | displayed in the UI                    |                            |
+-----------------------------+----------------------------------------+----------------------------+
| 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 | 0                          |
|                             | "PATH" and ".PY" to "PATHEXT"          |                            |
+-----------------------------+----------------------------------------+----------------------------+
| Shortcuts                   | Create shortcuts for the interpreter,  | 1                          |
|                             | documentation and IDLE if installed.   |                            |
+-----------------------------+----------------------------------------+----------------------------+
| Include_doc                 | 安裝Python文件                         | 1                          |
+-----------------------------+----------------------------------------+----------------------------+
| Include_debug               | Install debug binaries                 | 0                          |
+-----------------------------+----------------------------------------+----------------------------+
| Include_dev                 | Install developer headers and          | 1                          |
|                             | libraries                              |                            |
+-----------------------------+----------------------------------------+----------------------------+
| Include_exe                 | Install "python.exe" and related files | 1                          |
+-----------------------------+----------------------------------------+----------------------------+
| Include_launcher            | Install Python Launcher for Windows.   | 1                          |
+-----------------------------+----------------------------------------+----------------------------+
| InstallLauncherAllUsers     | Installs Python Launcher for Windows   | 1                          |
|                             | for all users.                         |                            |
+-----------------------------+----------------------------------------+----------------------------+
| Include_lib                 | Install standard library and extension | 1                          |
|                             | modules                                |                            |
+-----------------------------+----------------------------------------+----------------------------+
| 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  | 0                          |
|                             | override most other options.           |                            |
+-----------------------------+----------------------------------------+----------------------------+
| SimpleInstall               | Disable most install UI                | 0                          |
+-----------------------------+----------------------------------------+----------------------------+
| SimpleInstallDescription    | A custom message to display when the   | (empty)                    |
|                             | simplified install UI is used.         |                            |
+-----------------------------+----------------------------------------+----------------------------+

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

   python-3.9.0.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-3.9.0.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-3.9.0.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-3.9.0.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 3.9" 。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。

所有这三个命令也可以使用版本号后缀，例如， "python3.exe" 和
"python3.x.exe" 以及 "python.exe" （其中 "3.x" 是您要启动的特定版本，
例如 3.9 ）。在 "设置-->主页-->应用和功能" 页面中，点选 "管理可选功能"
，选择与每个命令关联的python版本。建议确保 "pip" 和 "idle" 与选择的
"python" 版本一致。

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" 。

"py.exe" 启动器将检测此 Python 安装版，但会优先使用来自传统安装器的安
装版。

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
-----------------

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 3.9;%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 3.9


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 3.9)
you will have noticed that Python 3.9 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
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

在某些情况下，可以在命令中包含版本限定符，以指定命令将使用哪个Python版
本。版本限定符以主版本号开头，可以选择后跟 ('.') 和次版本说明符。此外
，可以通过添加 "-32" 或 “-64” 来指定是请求32位还是64位实现。

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.
