Python 2。3. Python。X是不同的。如果您想下载Python 2的新版本，只需下载并安装新版本即可。

如果你想安装Python 3，你可以单独安装Python 3，然后更改Python 2的路径。3.使用Python。>所有控制面板项>系统>高级系统设置>环境变量。

每一个小版本的Python，都是任意3。X和2。X版本，将与其他版本并排安装在您的计算机上。只有补丁版本才会升级现有的安装。

因此，如果你想保留你已经安装的Python 2.7，那么就让它继续使用安装程序安装一个新版本。如果你想摆脱Python 2.7，你可以在安装新版本之前或之后卸载它——这没有区别。

Current Python 3 installations come with the py.exe launcher, which by default is installed into the system directory. This makes it available from the PATH, so you can automatically run it from any shell just by using py instead of python as the command. This avoids you having to put the current Python installation into PATH yourself. That way, you can easily have multiple Python installations side-by-side without them interfering with each other. When running, just use py script.py instead of python script.py to use the launcher. You can also specify a version using for example py -3 or py -3.6 to launch a specific version, otherwise the launcher will use the current default (which will usually be the latest 3.x).

如果你决定继续安装Python 2.7，你也可以使用启动器运行Python 2脚本(通常语法与Python 3不兼容)。只需使用py -2 script.py启动一个脚本。

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As for PyPI packages, every Python installation comes with its own folder where modules are installed into. So if you install a new version and you want to use modules you installed for a previous version, you will have to install them first for the new version. Current versions of the installer also offer you to install pip; it’s enabled by default, so you already have pip for every installation. Unless you explicitly add a Python installation to the PATH, you cannot just use pip though. Luckily, you can also simply use the py.exe launcher for this: py -m pip runs pip. So for example to install Beautiful Soup for Python 3.6, you could run py -3.6 -m pip install beautifulsoup4.

在2019年，你可以使用巧克力安装。打开你的cmd或powershell，输入:

choco install python

使用Chocolatey Windows包管理器安装/升级Python

假设你有Python 2.7.16:

C:\Windows\system32>python --version
python2 2.7.16

.．.你想升级到(现在的)3.x。y的版本。有一种简单的方法来安装Python 3.x的并行安装。y使用Windows包管理工具。

现在，现代Windows有了包管理，就像Debian Linux发行版有了apt-get, RedHat有了dnf一样:我们可以让它为我们工作!它叫Chocolatey。

巧克力色是什么?

Chocolatey是一个可编写脚本的命令行工具，它基于。net 4.0和烘焙到Visual Studio中的nuget包管理器。

如果你想了解Chocolatey以及为什么要使用它，一些正在阅读这篇文章的人可能会觉得特别有用，请访问https://chocolatey.org/docs/why

安装巧克力色

要获得巧克力包装管理器，您需要遵循https://chocolatey.org/docs/installation#installing-chocolatey中描述的流程，

我在这里总结一下。基本上有两个选项:使用cmd提示符，或使用PowerShell提示符。

CMD提示Chocolatey安装

启动管理命令提示符。在Windows 10上，要做到这一点:

Windows + R 键入cmd 按Ctrl + Shift +(返回

如果您在系统中没有管理员权限，请访问Chocolatey网站。您可能也不是完全没有运气，可以执行有限的本地安装，但我在这里不讨论这个问题。

将下面的字符串复制到命令提示符中，然后输入Enter:

@"%SystemRoot%\System32\WindowsPowerShell\v1.0\powershell.exe" -NoProfile -InputFormat None -ExecutionPolicy Bypass -Command "iex ((New-Object System.Net.WebClient).DownloadString('https://chocolatey.org/install.ps1'))" && SET "PATH=%PATH%;%ALLUSERSPROFILE%\chocolatey\bin"

Chocolatey将按以下方式下载并安装:

Getting latest version of the Chocolatey package for download.
Getting Chocolatey from https://chocolatey.org/api/v2/package/chocolatey/0.10.11.
Downloading 7-Zip commandline tool prior to extraction.
Extracting C:\Users\blahblahblah\AppData\Local\Temp\chocolatey\chocInstall\chocolatey.zip to C:\Users\blahblahblah\AppData\Local\Temp\chocolatey\chocInstall...
Installing chocolatey on this machine
Creating ChocolateyInstall as an environment variable (targeting 'Machine')
  Setting ChocolateyInstall to 'C:\ProgramData\chocolatey'
WARNING: It's very likely you will need to close and reopen your shell
  before you can use choco.
Restricting write permissions to Administrators
We are setting up the Chocolatey package repository.
The packages themselves go to 'C:\ProgramData\chocolatey\lib'
  (i.e. C:\ProgramData\chocolatey\lib\yourPackageName).
A shim file for the command line goes to 'C:\ProgramData\chocolatey\bin'
  and points to an executable in 'C:\ProgramData\chocolatey\lib\yourPackageName'.

Creating Chocolatey folders if they do not already exist.

WARNING: You can safely ignore errors related to missing log files when
  upgrading from a version of Chocolatey less than 0.9.9.
  'Batch file could not be found' is also safe to ignore.
  'The system cannot find the file specified' - also safe.
chocolatey.nupkg file not installed in lib.
 Attempting to locate it from bootstrapper.
PATH environment variable does not have C:\ProgramData\chocolatey\bin in it. Adding...
WARNING: Not setting tab completion: Profile file does not exist at 'C:\Users\blahblahblah\Documents\WindowsPowerShell\Microsoft.PowerShell_profile.ps1'.
Chocolatey (choco.exe) is now ready.
You can call choco from anywhere, command line or powershell by typing choco.
Run choco /? for a list of functions.
You may need to shut down and restart powershell and/or consoles
 first prior to using choco.
Ensuring chocolatey commands are on the path
Ensuring chocolatey.nupkg is in the lib folder

退出CMD提示符或输入以下命令重新加载环境变量:

refreshenv

PowerShell Chocolatey安装

如果你更喜欢PowerShell而不是cmd提示符，你可以直接从那里做这件事，但是你必须告诉PowerShell运行一个适当的脚本执行策略，让它工作。在Windows 10上，我发现最简单的方法是在Windows按钮旁边的Cortana搜索栏中输入以下内容:

PowerShell.exe

接下来，右键单击弹出菜单中的“最佳匹配”选项，并选择“以管理员身份运行”

现在你在PowerShell中，希望以管理员权限运行，执行以下命令来安装Chocolatey:

Set-ExecutionPolicy Bypass -Scope Process -Force; iex ((New-Object System.Net.WebClient).DownloadString('https://chocolatey.org/install.ps1'))

PowerShell将为您下载Chocolatey并启动安装。只需要几分钟。它看起来完全像CMD安装，保存一些花哨的彩色文本。

退出PowerShell或输入以下命令重新加载环境变量:

refreshenv

Python升级

无论您使用PowerShell还是cmd提示符，choco命令都是相同的。使用上面的说明启动你最喜欢的。我将使用管理员cmd提示符:

C:\WINDOWS\system32>choco upgrade python -y

本质上，chocolatey会告诉你“嘿，Python没有安装”，因为你是从2.7开始的。X，它将2.7版本视为完全独立的。它只会给你最新的版本，3.x。Y(在撰写本文时，是3.7.2，但几个月后会有所改变):

Chocolatey v0.10.11
Upgrading the following packages:
python
By upgrading you accept licenses for the packages.
python is not installed. Installing...

python3 v3.x.y [Approved]
python3 package files upgrade completed. Performing other installation steps.
Installing 64-bit python3...
python3 has been installed.
Installed to: 'C:\Python37' 
  python3 can be automatically uninstalled.
Environment Vars (like PATH) have changed. Close/reopen your shell to
 see the changes (or in powershell/cmd.exe just type `refreshenv`).
 The upgrade of python3 was successful.
  Software installed as 'exe', install location is likely default.

python v3.x.y [Approved]
python package files upgrade completed. Performing other installation steps.
 The upgrade of python was successful.
  Software install location not explicitly set, could be in package or
  default install location if installer.

Chocolatey upgraded 2/2 packages.
 See the log for details (C:\ProgramData\chocolatey\logs\chocolatey.log).

退出cmd/Powershell提示符并重新输入，或者使用refreshenv，然后输入py——version

C:\Windows\System32>refreshenv
Refreshing environment variables from registry for cmd.exe. Please wait...Finished..

C:\Windows\system32>py --version
Python 3.7.2

请注意，当您在命令行输入Python时，最新的Python安装现在将接管。可以通过以下命令运行任意一个版本:

py -2
Python 2.7.16 (v2.7.16:413a49145e, Mar  4 2019, 01:37:19) [MSC v.1500 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> exit()

C:\>py -3
Python 3.7.2 (tags/v3.7.2:9a3ffc0492, Dec 23 2018, 23:09:28) [MSC v.1916 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>>exit()
C:\>

从这里开始，我建议您使用Python pip实用程序来安装所需的任何包。例如，假设您想要安装Flask。下面的命令首先升级pip，然后安装Flask

C:\>py -3 -m pip install --upgrade pip
Collecting pip
  Downloading https://files.pythonhosted.org/packages/d8/f3/413bab4ff08e1fc4828dfc59996d721917df8e8583ea85385d51125dceff/pip-19.0.3-py2.py3-none-any.whl (1.4MB)
    100% |████████████████████████████████| 1.4MB 1.6MB/s
Installing collected packages: pip
  Found existing installation: pip 18.1
    Uninstalling pip-18.1:
      Successfully uninstalled pip-18.1
Successfully installed pip-19.0.3

c:\>py -3 -m pip install Flask

.．.会成功的。python快乐!

如果您正在升级任何3.x。Y到3.x。z (patch) Python版本，只需进入Python下载页面获取最新版本并开始安装。因为你的机器上已经安装了Python，安装程序会提示你“立即升级”。单击该按钮，它将用一个新版本替换现有版本。安装后还必须重新启动计算机。

如果你从3升级。X到3。y(未成年人)，然后会提示“现在安装”。在这种情况下，您不是在升级，而是在安装Python的新版本。您的机器上可以安装多个版本。它们将位于不同的目录中。当你的机器上有多个Python版本时，你需要使用py启动器来启动特定版本的Python。

例如:

py -3.7

or

py -3.8

确保在您的机器上安装了py启动器。如果您使用windows安装程序的默认设置，它将自动安装。如果你在安装窗口上点击“自定义安装”链接，你可以随时检查它。

如果你的机器上安装了几个Python版本，并且你有一个项目正在使用以前版本的Python，使用虚拟环境，例如(venv)，你可以在venv中使用以下方法升级Python:

升级你的虚拟环境路径

例如，我的./venv虚拟环境中有Python 3.7，我想将venv升级到Python 3.8，我会做以下工作

Python -m venv——upgrade ./venv

只要安装python最新版本的安装程序，它就会自动检测你的python版本，并提示升级python并开始升级

你可以使用pyenv。它可以让你轻松地在python的所有版本之间切换。

对我来说，一个快速而无痛的方法是这样做:

在我受影响的环境上执行pip freeze > requirements.txt(或任何您想要备份您的需求的方法) 删除旧版本的Python(在我的情况下是3.8) 移除相关的环境 安装新版本(在我的例子中是3.9.5) 重新创建我的环境python -m venv venv或任何您希望的方式 重新安装我的插件/应用程序pip install -r requirements.txt或任何你想要的

我能够使用以下命令执行PowerShell，并且python升级没有问题。Python -m PIP install——upgrade PIP please see image

现在你只需要从微软商店安装几个Python版本就可以了。这些都是由Python软件基金会发布的。

https://apps.microsoft.com/store/search?hl=en-en&gl=EN&publisher=Python%20Software%20Foundation