切换 Homebrew 安装的 Python 版本 (3.9 → 3.8)
Switching Python version (3.9 → 3.8) installed by Homebrew
这与 的情况非常相似，但反之亦然。我通过 Homebrew 安装了 Python 3.8 并将其更新为 3.9:
% brew list --formula | grep python
python@3.8
python@3.9
我想使用 Python 3.8 作为带有 python3 命令的默认版本，并尝试了 - 受 启发 - 以下内容：
brew unlink python@3.9
brew unlink python@3.8
brew link python@3.8
最后给了我以下输出：
% brew link python@3.8
Linking /usr/local/Cellar/python@3.8/3.8.6_2...
Error: Could not symlink bin/pip3
Target /usr/local/bin/pip3
already exists. You may want to remove it:
rm '/usr/local/bin/pip3'
To force the link and overwrite all conflicting files:
brew link --overwrite python@3.8
To list all files that would be deleted:
brew link --overwrite --dry-run python@3.8
所以我做到了：
% brew link --overwrite --dry-run python@3.8
Would remove:
/usr/local/bin/pip3
If you need to have this software first in your PATH instead consider running:
echo 'export PATH="/usr/local/opt/python@3.8/bin:$PATH"' >> ~/.zshrc
我认为最好先检查一下：
ralf@razbook ~ % brew link --force --dry-run python@3.8
Would link:
/usr/local/bin/2to3
/usr/local/bin/2to3-3.8
/usr/local/bin/easy_install-3.8
/usr/local/bin/idle3
/usr/local/bin/idle3.8
/usr/local/bin/pip3
/usr/local/bin/pip3.8
/usr/local/bin/pydoc3
/usr/local/bin/pydoc3.8
/usr/local/bin/python3
/usr/local/bin/python3-config
/usr/local/bin/python3.8
/usr/local/bin/python3.8-config
/usr/local/bin/wheel3
/usr/local/share/man/man1/python3.1
/usr/local/share/man/man1/python3.8.1
/usr/local/lib/pkgconfig/python-3.8-embed.pc
/usr/local/lib/pkgconfig/python-3.8.pc
/usr/local/lib/pkgconfig/python3-embed.pc
/usr/local/lib/pkgconfig/python3.pc
/usr/local/Frameworks/Python.framework/Headers
/usr/local/Frameworks/Python.framework/Python
/usr/local/Frameworks/Python.framework/Resources
/usr/local/Frameworks/Python.framework/Versions/3.8
/usr/local/Frameworks/Python.framework/Versions/Current
If you need to have this software first in your PATH instead consider running:
echo 'export PATH="/usr/local/opt/python@3.8/bin:$PATH"' >> ~/.zshrc
听起来不错，让我们开始吧：
% brew link --force python@3.8
Linking /usr/local/Cellar/python@3.8/3.8.6_2...
Error: Could not symlink bin/pip3
Target /usr/local/bin/pip3
already exists. You may want to remove it:
rm '/usr/local/bin/pip3'
To force the link and overwrite all conflicting files:
brew link --overwrite python@3.8
To list all files that would be deleted:
brew link --overwrite --dry-run python@3.8
可惜我跳过了dry-运行:
% brew link --overwrite python@3.8
Linking /usr/local/Cellar/python@3.8/3.8.6_2... 25 symlinks created
If you need to have this software first in your PATH instead consider running:
echo 'export PATH="/usr/local/opt/python@3.8/bin:$PATH"' >> ~/.zshrc
有些事情似乎奏效了：
% python3 --version
Python 3.8.6
% pip3 --version
pip 20.2.4 from /usr/local/lib/python3.8/site-packages/pip (python 3.8)
但是 pipenv 还是有问题：
% pipenv install google-ads
Warning: Python 3.9 was not found on your system...
Neither 'pyenv' nor 'asdf' could be found to install Python.
You can specify specific versions of Python with:
$ pipenv --python path/to/python
也许我应该重新安装 pipenv?
% which pipenv
/usr/local/bin/pipenv
% pip3 uninstall pipenv
Found existing installation: pipenv 2020.8.13
Uninstalling pipenv-2020.8.13:
Would remove:
/usr/local/bin/pipenv
/usr/local/bin/pipenv-resolver
/usr/local/lib/python3.8/site-packages/pipenv-2020.8.13.dist-info/*
/usr/local/lib/python3.8/site-packages/pipenv/*
Proceed (y/n)? y
Successfully uninstalled pipenv-2020.8.13
% pip3 install pipenv
Collecting pipenv
Downloading pipenv-2020.11.15-py2.py3-none-any.whl (3.9 MB)
|████████████████████████████████| 3.9 MB 2.9 MB/s
Requirement already satisfied: pip>=18.0 in /usr/local/lib/python3.8/site-packages (from pipenv) (20.2.4)
Requirement already satisfied: virtualenv in /usr/local/lib/python3.8/site-packages (from pipenv) (20.0.31)
Requirement already satisfied: setuptools>=36.2.1 in /usr/local/lib/python3.8/site-packages (from pipenv) (50.3.2)
Requirement already satisfied: certifi in /usr/local/lib/python3.8/site-packages (from pipenv) (2020.6.20)
Requirement already satisfied: virtualenv-clone>=0.2.5 in /usr/local/lib/python3.8/site-packages (from pipenv) (0.5.4)
Requirement already satisfied: distlib<1,>=0.3.1 in /usr/local/lib/python3.8/site-packages (from virtualenv->pipenv) (0.3.1)
Requirement already satisfied: filelock<4,>=3.0.0 in /usr/local/lib/python3.8/site-packages (from virtualenv->pipenv) (3.0.12)
Collecting six<2,>=1.9.0
Using cached six-1.15.0-py2.py3-none-any.whl (10 kB)
Requirement already satisfied: appdirs<2,>=1.4.3 in /usr/local/lib/python3.8/site-packages (from virtualenv->pipenv) (1.4.4)
Installing collected packages: pipenv, six
Successfully installed pipenv-2020.11.15 six-1.15.0
但仍然：
% pipenv install google-ads
Warning: Python 3.9 was not found on your system...
Neither 'pyenv' nor 'asdf' could be found to install Python.
You can specify specific versions of Python with:
$ pipenv --python path/to/python
实际上不行，但让我们声明 Python pipenv 应该使用：
% pipenv --python /usr/local/opt/python@3.8/bin/python3 install google-ads
Creating a virtualenv for this project...
Pipfile: /Users/ralf/code/test_snippets/20-12-10_google_ads/Pipfile
Using /usr/local/opt/python@3.8/bin/python3 (3.8.6) to create virtualenv...
⠦ Creating virtual environment...created virtual environment CPython3.8.6.final.0-64 in 362ms
creator CPython3Posix(dest=/Users/ralf/.local/share/virtualenvs/20-12-10_google_ads-S7vGVfKj, clear=False, global=False)
seeder FromAppData(download=False, pip=bundle, setuptools=bundle, wheel=bundle, via=copy, app_data_dir=/Users/ralf/Library/Application Support/virtualenv)
added seed packages: pip==20.2.4, setuptools==50.3.2, wheel==0.35.1
activators BashActivator,CShellActivator,FishActivator,PowerShellActivator,PythonActivator,XonshActivator
✔ Successfully created virtual environment!
Virtualenv location: /Users/ralf/.local/share/virtualenvs/20-12-10_google_ads-S7vGVfKj
Warning: Your Pipfile requires python_version 3.9, but you are using 3.8.6 (/Users/ralf/.local/share/v/2/bin/python).
$ pipenv --rm and rebuilding the virtual environment may resolve the issue.
$ pipenv check will surely fail.
Warning: Your Pipfile requires python_version 3.9, but you are using 3.8.6 (/Users/ralf/.local/share/v/2/bin/python).
$ pipenv --rm and rebuilding the virtual environment may resolve the issue.
$ pipenv check will surely fail.
Installing google-ads...
pipenv --rm 并且重建虚拟环境没有帮助。 （我什至考虑简单地卸载 Python 3.9 并再次安装 Python 3.8 – 但是 don't know how。）
有没有办法说服 pipenv 使用 Python 3.8？
好吧，有时候提出问题有助于自己找到解决方案 – 顺便说一下，Whosebug 的一大优点。
提示在 pipenv 的警告中：“您的 Pipfile 需要 python_version 3.9”。
我只是做了
rm Pipfile
rm Pipfile.lock
然后成功了：
pipenv install google-ads
好吧，至少 pipenv 在 Python 3.8 中可以正常工作。 google-ads 仍然存在问题，但那是 。
可能更改 Pipfile 就足够了：
[requires]
python_version = "3.8"
很高兴您能够以自己的方式解决问题，但让我添加一些建议。一般来说，降级 Python（或任何程序）通常不受支持。升级可能会升级其他包中的依赖项，这些依赖项不向后兼容 Python 的旧版本或其他依赖项。简而言之，您 不应该 甚至想要“降级”软件包。
相反，您应该使用多个独立的环境，例如使用 virtualenv 这样，如果您出于某种原因 需要 一个较低版本，您可以用一个新的较低版本替换整个环境（请注意与“降级”的细微差别，因为您正在完全使用新环境）。
这与
% brew list --formula | grep python
python@3.8
python@3.9
我想使用 Python 3.8 作为带有 python3 命令的默认版本，并尝试了 - 受
brew unlink python@3.9
brew unlink python@3.8
brew link python@3.8
最后给了我以下输出：
% brew link python@3.8
Linking /usr/local/Cellar/python@3.8/3.8.6_2...
Error: Could not symlink bin/pip3
Target /usr/local/bin/pip3
already exists. You may want to remove it:
rm '/usr/local/bin/pip3'
To force the link and overwrite all conflicting files:
brew link --overwrite python@3.8
To list all files that would be deleted:
brew link --overwrite --dry-run python@3.8
所以我做到了：
% brew link --overwrite --dry-run python@3.8
Would remove:
/usr/local/bin/pip3
If you need to have this software first in your PATH instead consider running:
echo 'export PATH="/usr/local/opt/python@3.8/bin:$PATH"' >> ~/.zshrc
我认为最好先检查一下：
ralf@razbook ~ % brew link --force --dry-run python@3.8
Would link:
/usr/local/bin/2to3
/usr/local/bin/2to3-3.8
/usr/local/bin/easy_install-3.8
/usr/local/bin/idle3
/usr/local/bin/idle3.8
/usr/local/bin/pip3
/usr/local/bin/pip3.8
/usr/local/bin/pydoc3
/usr/local/bin/pydoc3.8
/usr/local/bin/python3
/usr/local/bin/python3-config
/usr/local/bin/python3.8
/usr/local/bin/python3.8-config
/usr/local/bin/wheel3
/usr/local/share/man/man1/python3.1
/usr/local/share/man/man1/python3.8.1
/usr/local/lib/pkgconfig/python-3.8-embed.pc
/usr/local/lib/pkgconfig/python-3.8.pc
/usr/local/lib/pkgconfig/python3-embed.pc
/usr/local/lib/pkgconfig/python3.pc
/usr/local/Frameworks/Python.framework/Headers
/usr/local/Frameworks/Python.framework/Python
/usr/local/Frameworks/Python.framework/Resources
/usr/local/Frameworks/Python.framework/Versions/3.8
/usr/local/Frameworks/Python.framework/Versions/Current
If you need to have this software first in your PATH instead consider running:
echo 'export PATH="/usr/local/opt/python@3.8/bin:$PATH"' >> ~/.zshrc
听起来不错，让我们开始吧：
% brew link --force python@3.8
Linking /usr/local/Cellar/python@3.8/3.8.6_2...
Error: Could not symlink bin/pip3
Target /usr/local/bin/pip3
already exists. You may want to remove it:
rm '/usr/local/bin/pip3'
To force the link and overwrite all conflicting files:
brew link --overwrite python@3.8
To list all files that would be deleted:
brew link --overwrite --dry-run python@3.8
可惜我跳过了dry-运行:
% brew link --overwrite python@3.8
Linking /usr/local/Cellar/python@3.8/3.8.6_2... 25 symlinks created
If you need to have this software first in your PATH instead consider running:
echo 'export PATH="/usr/local/opt/python@3.8/bin:$PATH"' >> ~/.zshrc
有些事情似乎奏效了：
% python3 --version
Python 3.8.6
% pip3 --version
pip 20.2.4 from /usr/local/lib/python3.8/site-packages/pip (python 3.8)
但是 pipenv 还是有问题：
% pipenv install google-ads
Warning: Python 3.9 was not found on your system...
Neither 'pyenv' nor 'asdf' could be found to install Python.
You can specify specific versions of Python with:
$ pipenv --python path/to/python
也许我应该重新安装 pipenv?
% which pipenv
/usr/local/bin/pipenv
% pip3 uninstall pipenv
Found existing installation: pipenv 2020.8.13
Uninstalling pipenv-2020.8.13:
Would remove:
/usr/local/bin/pipenv
/usr/local/bin/pipenv-resolver
/usr/local/lib/python3.8/site-packages/pipenv-2020.8.13.dist-info/*
/usr/local/lib/python3.8/site-packages/pipenv/*
Proceed (y/n)? y
Successfully uninstalled pipenv-2020.8.13
% pip3 install pipenv
Collecting pipenv
Downloading pipenv-2020.11.15-py2.py3-none-any.whl (3.9 MB)
|████████████████████████████████| 3.9 MB 2.9 MB/s
Requirement already satisfied: pip>=18.0 in /usr/local/lib/python3.8/site-packages (from pipenv) (20.2.4)
Requirement already satisfied: virtualenv in /usr/local/lib/python3.8/site-packages (from pipenv) (20.0.31)
Requirement already satisfied: setuptools>=36.2.1 in /usr/local/lib/python3.8/site-packages (from pipenv) (50.3.2)
Requirement already satisfied: certifi in /usr/local/lib/python3.8/site-packages (from pipenv) (2020.6.20)
Requirement already satisfied: virtualenv-clone>=0.2.5 in /usr/local/lib/python3.8/site-packages (from pipenv) (0.5.4)
Requirement already satisfied: distlib<1,>=0.3.1 in /usr/local/lib/python3.8/site-packages (from virtualenv->pipenv) (0.3.1)
Requirement already satisfied: filelock<4,>=3.0.0 in /usr/local/lib/python3.8/site-packages (from virtualenv->pipenv) (3.0.12)
Collecting six<2,>=1.9.0
Using cached six-1.15.0-py2.py3-none-any.whl (10 kB)
Requirement already satisfied: appdirs<2,>=1.4.3 in /usr/local/lib/python3.8/site-packages (from virtualenv->pipenv) (1.4.4)
Installing collected packages: pipenv, six
Successfully installed pipenv-2020.11.15 six-1.15.0
但仍然：
% pipenv install google-ads
Warning: Python 3.9 was not found on your system...
Neither 'pyenv' nor 'asdf' could be found to install Python.
You can specify specific versions of Python with:
$ pipenv --python path/to/python
实际上不行，但让我们声明 Python pipenv 应该使用：
% pipenv --python /usr/local/opt/python@3.8/bin/python3 install google-ads
Creating a virtualenv for this project...
Pipfile: /Users/ralf/code/test_snippets/20-12-10_google_ads/Pipfile
Using /usr/local/opt/python@3.8/bin/python3 (3.8.6) to create virtualenv...
⠦ Creating virtual environment...created virtual environment CPython3.8.6.final.0-64 in 362ms
creator CPython3Posix(dest=/Users/ralf/.local/share/virtualenvs/20-12-10_google_ads-S7vGVfKj, clear=False, global=False)
seeder FromAppData(download=False, pip=bundle, setuptools=bundle, wheel=bundle, via=copy, app_data_dir=/Users/ralf/Library/Application Support/virtualenv)
added seed packages: pip==20.2.4, setuptools==50.3.2, wheel==0.35.1
activators BashActivator,CShellActivator,FishActivator,PowerShellActivator,PythonActivator,XonshActivator
✔ Successfully created virtual environment!
Virtualenv location: /Users/ralf/.local/share/virtualenvs/20-12-10_google_ads-S7vGVfKj
Warning: Your Pipfile requires python_version 3.9, but you are using 3.8.6 (/Users/ralf/.local/share/v/2/bin/python).
$ pipenv --rm and rebuilding the virtual environment may resolve the issue.
$ pipenv check will surely fail.
Warning: Your Pipfile requires python_version 3.9, but you are using 3.8.6 (/Users/ralf/.local/share/v/2/bin/python).
$ pipenv --rm and rebuilding the virtual environment may resolve the issue.
$ pipenv check will surely fail.
Installing google-ads...
pipenv --rm 并且重建虚拟环境没有帮助。 （我什至考虑简单地卸载 Python 3.9 并再次安装 Python 3.8 – 但是 don't know how。）
有没有办法说服 pipenv 使用 Python 3.8？
好吧，有时候提出问题有助于自己找到解决方案 – 顺便说一下，Whosebug 的一大优点。
提示在 pipenv 的警告中：“您的 Pipfile 需要 python_version 3.9”。
我只是做了
rm Pipfile
rm Pipfile.lock
然后成功了：
pipenv install google-ads
好吧，至少 pipenv 在 Python 3.8 中可以正常工作。 google-ads 仍然存在问题，但那是
可能更改 Pipfile 就足够了：
[requires]
python_version = "3.8"
很高兴您能够以自己的方式解决问题，但让我添加一些建议。一般来说，降级 Python（或任何程序）通常不受支持。升级可能会升级其他包中的依赖项，这些依赖项不向后兼容 Python 的旧版本或其他依赖项。简而言之，您 不应该 甚至想要“降级”软件包。
相反，您应该使用多个独立的环境，例如使用 virtualenv 这样，如果您出于某种原因 需要 一个较低版本，您可以用一个新的较低版本替换整个环境（请注意与“降级”的细微差别，因为您正在完全使用新环境）。