【Mac】【Homebrew】【Python】安装 Python@2 问题汇总

 

目录

一. 问题

二. 分析

2.1 系统环境

2.2 Cellar Python

三. 查找

3.1 formula  和 cask

3.2 python@2 delete

四. 解决

五. 参考

---

 

一. 问题

最近折腾 Python 环境有些需要在 Python@2 环境下才能进行，今天用 brew upgrade 后，发现 python@2 咋没了？

没办法，我猜 brew 的python@2 可能出问题了，卸载再安装报如下错误？

# 查找
$ brew search python@2
Error: No formulae or casks found for "python@2".


# 安装
$ brew install python@2
==> Searching for similarly named formulae...
Error: No similarly named formulae found.
Error: No available formula or cask with the name "python@2".
==> Searching for a previously deleted formula (in the last month)...
Error: No previously deleted formula found.
==> Searching taps on GitHub...
Error: No formulae found in taps.

以前好好的，咋安装不上了呢 ？

 

二. 分析

2.1 系统环境

首先，看看本机环境都有哪些 python 版本：

# 本机环境版本
$ python --version
Python 2.7.16

# 本机环境，脚本命令路径
$ which python
/usr/bin/python


## python2，脚本命令路径
$ which python2
/usr/local/bin/python2

## python3，脚本命令路径
$ which python3
/usr/local/bin/python3

查看本机环境链接的脚本路径：

# 本机环境链接的系统Python 版本
$ ls -al /usr/bin/python*
lrwxr-xr-x  1 root  wheel     75 10 11  2019 /usr/bin/python -> ../../System/Library/Frameworks/Python.framework/Versions/2.7/bin/python2.7
lrwxr-xr-x  1 root  wheel     82 10 11  2019 /usr/bin/python-config -> ../../System/Library/Frameworks/Python.framework/Versions/2.7/bin/python2.7-config
lrwxr-xr-x  1 root  wheel     75 10 11  2019 /usr/bin/python2 -> ../../System/Library/Frameworks/Python.framework/Versions/2.7/bin/python2.7
lrwxr-xr-x  1 root  wheel     75 10 11  2019 /usr/bin/python2.7 -> ../../System/Library/Frameworks/Python.framework/Versions/2.7/bin/python2.7
lrwxr-xr-x  1 root  wheel     82 10 11  2019 /usr/bin/python2.7-config -> ../../System/Library/Frameworks/Python.framework/Versions/2.7/bin/python2.7-config
-rwxr-xr-x  1 root  wheel  31488  3 17  2020 /usr/bin/python3
lrwxr-xr-x  1 root  wheel     76 10 11  2019 /usr/bin/pythonw -> ../../System/Library/Frameworks/Python.framework/Versions/2.7/bin/pythonw2.7
lrwxr-xr-x  1 root  wheel     76 10 11  2019 /usr/bin/pythonw2.7 -> ../../System/Library/Frameworks/Python.framework/Versions/2.7/bin/pythonw2.7

可见，系统真实的引用路径为：

/System/Library/Frameworks/Python.framework/Versions/2.7/

系统本机环境提供的 python 版本不建议进行安装各种第三方和更新 python 版本，以免引起不必要的不可预见的麻烦;

推荐 brew install python 方式，然后使用virtualenv 虚拟环境方式，配置各个项目运行空间;

 

2.2 Cellar Python

查看一下 python2 和 python3 引用的路径：

$ ls -al /usr/local/bin/python*
lrwxr-xr-x  1 root      admin  18 12 20  2018 /usr/local/bin/python2 -> /usr/bin/python2.7
lrwxr-xr-x  1 xxx  admin  40  5 18 10:19 /usr/local/bin/python3 -> ../Cellar/[email protected]/3.9.1_8/bin/python3
lrwxr-xr-x  1 xxx  admin  47  5 18 10:19 /usr/local/bin/python3-config -> ../Cellar/[email protected]/3.9.1_8/bin/python3-config
lrwxr-xr-x  1 xxx  admin  40  1 14 18:06 /usr/local/bin/python3.8 -> ../Cellar/[email protected]/3.8.5/bin/python3.8
lrwxr-xr-x  1 xxx  admin  47  1 14 18:06 /usr/local/bin/python3.8-config -> ../Cellar/[email protected]/3.8.5/bin/python3.8-config
lrwxr-xr-x  1 xxx  admin  42  5 18 10:19 /usr/local/bin/python3.9 -> ../Cellar/[email protected]/3.9.1_8/bin/python3.9
lrwxr-xr-x  1 xxx  admin  49  5 18 10:19 /usr/local/bin/python3.9-config -> ../Cellar/[email protected]/3.9.1_8/bin/python3.9-config

目前发现，python3.x 版本链接的都是 homebrew 中安装的；但是 python2 之前卸载掉后，通过 homebrew 安装不上了，然后链接为本机系统的 python2.x 版本;

 

查看一下，各个python 版本的 pip 版本：

# python2 pip version
$ python2 -m pip --version
/System/Library/Frameworks/Python.framework/Versions/2.7/Resources/Python.app/Contents/MacOS/Python: No module named pip

# python3 pip version
$ python3 -m pip --version
pip 21.0.1 from /usr/local/lib/python3.9/site-packages/pip (python 3.9)

目前发现，系统环境 Python 2.7.16 版本的 Python2.x 没有安装 pip;

注意：

macOS 系统Python 不提供pip 。如果需要，请按照pip 文档 为系统Python 安装它。

 

三. 查找

从如上分析看来，需要做如下步骤：

1. 通过 Homebrew 安装 python@2；
2. 如若无法安装，查找一下原因所在；
3. 如果安装成功，查看一下有没有 pip 包;

目前看来，步骤三是行不通的;

 

去Python 官网，https://www.python.org/downloads/ 发现如下信息:

Python 2.7是Python 2.x系列的结尾；作为2.x系列的最后一个版本，Python 2.7 在2020年之前获得了错误修复支持。

该支持在2020年1月1日正式停止，并且2.7.18 代码冻结在2020年1月1日发生，但最终版本在该日期之后发生。即不会有Python 2.8 版本；

哎，原来是官方不再支持和维护了;

 

3.1 formula  和 cask

formula  和 casks 如何翻译和如何区别：

formulae 意思是一些软件包(SDK)，一般是命令行工具、开发库、一些字体、插件，共性是不提供界面，提供给终端或者是开发者使用。

cask 是用户软件(APP)，比如 chrome、mvim、wechat、wechatwork 这些提供用户交互界面的软件。

把问题转向Homebrew Documentation -> Python 看看官网上对 Python 有啥说明没？

看到了如下说明:

Homebrew provided a python@2 formula until the end of 2019, at which point it was removed due to the Python 2 deprecation.

翻译：

Homebrew 提供了一个python@2 软件包,直到2019年底,由于Python 2 已被官方弃用,所以该软件包已被删除和不受支持。

 

Important: If you choose to use a Python which isn’t either of these two (system Python or brewed Python), the Homebrew team cannot support any breakage that may occur.

翻译:

如果您选择使用的Python不是这两种(系统Python或酿造Python)中的任何一种,那么Homebrew 团队将无法支持可能发生的任何损坏。

啥意思呢？

大致就是 Python 官网不再支持和维护 Python 2.x 了，那么 Homebrew 团队也将和官网同步不再支持和维护 Python 2.x 了，所以就从存储库里给删除了;

 

3.2 python@2 delete

那咋办 ？

我去 Homebrew Github   上列举了一些issue 信息:

1. https://github.com/Homebrew/brew/issues/7057
2. https://github.com/Homebrew/homebrew-core/issues/50546
3. https://github.com/Homebrew/brew/pull/7066
4. https://github.com/Homebrew/brew/pull/7019
5. https://github.com/Homebrew/homebrew-core/pull/49796

此处我个人是比较支持 50546  中，提问者观点的，然后看到 由于过于激烈而无法与合作者进行对话，此issue 被锁定，我就怂了；

只敢在此处吐槽一下:

一个软件在整个生命周期内，哪怕过了软件最迟寿命支持周期，只要有一定的存量用户(规模性比较大的场景)，原则上是不受支持的，但是道义上还是需要开个口子(给个继续使用的办法或升级到最新版本的方案，并行一段时间，或持续性特定版本后续不再维护，总之，有办法持续能用，但我不再维护。)支持一下的；

不能因为这个软件过时11 年了，有将近 10 年时间去更新到最新受官方支持的版本上去而打发人; 次观点我是不敢苟同(不是一个技术人该有的操作)，实际上，日常生活和商业环境中，还有大量过时的机器和软件系统在跑着上古代码呢？

微软的 XP 系统，虽然官方早就不再支持了，但到现在还有很多人使用呢？适用的典型场景有打印店...老破旧古董机器上跑新系统压根有些就跑不起来，旧设施硬件下不得不装旧系统，而且还是有办法装 XP 系统的;

 

四. 解决

参考:

1. https://stackoverflow.com/questions/60298514/how-to-reinstall-python2-from-homebrew

cd ~
wget https://raw.githubusercontent.com/Homebrew/homebrew-core/86a44a0a552c673a05f11018459c9f5faae3becc/Formula/[email protected]
brew install [email protected]
rm [email protected]

执行过程，如下:

# 1. 进入默认用户目录
$ cd ~

# 2. 下载 [email protected] 文件
$ wget https://raw.githubusercontent.com/Homebrew/homebrew-core/86a44a0a552c673a05f11018459c9f5faae3becc/Formula/[email protected]
--2021-05-18 16:47:21--  https://raw.githubusercontent.com/Homebrew/homebrew-core/86a44a0a552c673a05f11018459c9f5faae3becc/Formula/[email protected]
正在解析主机 raw.githubusercontent.com (raw.githubusercontent.com)... 185.199.109.133, 185.199.110.133, 185.199.108.133, ...
正在连接 raw.githubusercontent.com (raw.githubusercontent.com)|185.199.109.133|:443... 已连接。
已发出 HTTP 请求，正在等待回应... 200 OK
长度：13347 (13K) [text/plain]
正在保存至: “[email protected]”

[email protected]                          100%[====================================================================>]  13.03K  --.-KB/s  用时 0.002s  

2021-05-18 16:47:22 (6.84 MB/s) - 已保存 “[email protected]” [13347/13347])

# 3. 修改 [email protected] 文件权限(可选)
$ chmod 755 python\@2.rb

# 4. 删除系统默认 /usr/local/bin/python2 -> /usr/bin/python2.7(可选)
$ rm /usr/local/bin/python2

# 5. 安装 [email protected]
$ brew install [email protected]
Error: Failed to load cask: [email protected]
Cask 'python@2' is unreadable: wrong constant name #
Warning: Treating [email protected] as a formula.
==> Downloading https://homebrew.bintray.com/bottles/python%402-2.7.17_1.catalina.bottle.tar.gz
Already downloaded: /Users/dovsnier/Library/Caches/Homebrew/downloads/a4e7e62c67a0ffb99906cfde7bfaf5b028f31c44f5a5ec3aec49740205151fc5--python@2-2.7.17_1.catalina.bottle.tar.gz
==> Pouring [email protected]_1.catalina.bottle.tar.gz
==> /usr/local/Cellar/python@2/2.7.17_1/bin/python -s setup.py --no-user-cfg install --force --verbose --single-version-externally-managed --recor
==> /usr/local/Cellar/python@2/2.7.17_1/bin/python -s setup.py --no-user-cfg install --force --verbose --single-version-externally-managed --recor
==> /usr/local/Cellar/python@2/2.7.17_1/bin/python -s setup.py --no-user-cfg install --force --verbose --single-version-externally-managed --recor
==> Caveats
Pip and setuptools have been installed. To update them
  pip install --upgrade pip setuptools

You can install Python packages with
  pip install 

They will install into the site-package directory
  /usr/local/lib/python2.7/site-packages

See: https://docs.brew.sh/Homebrew-and-Python
==> Summary
  /usr/local/Cellar/python@2/2.7.17_1: 3,806 files, 51.7MB

# 6. 删除 [email protected] 文件
$ rm [email protected]

# 7. 如果有需要，卸载 [email protected](可选)
$ brew uninstall python\@2.rb

查看一下安装后，Python@2 引用：

$ ls -al /usr/local/bin/python*
lrwxr-xr-x  1 xxx  admin  38  5 18 17:03 /usr/local/bin/python -> ../Cellar/python@2/2.7.17_1/bin/python
lrwxr-xr-x  1 xxx  admin  45  5 18 17:03 /usr/local/bin/python-config -> ../Cellar/python@2/2.7.17_1/bin/python-config
lrwxr-xr-x  1 xxx  admin  39  5 18 17:03 /usr/local/bin/python2 -> ../Cellar/python@2/2.7.17_1/bin/python2
lrwxr-xr-x  1 xxx  admin  46  5 18 17:03 /usr/local/bin/python2-config -> ../Cellar/python@2/2.7.17_1/bin/python2-config
lrwxr-xr-x  1 xxx  admin  41  5 18 17:03 /usr/local/bin/python2.7 -> ../Cellar/python@2/2.7.17_1/bin/python2.7
lrwxr-xr-x  1 xxx  admin  48  5 18 17:03 /usr/local/bin/python2.7-config -> ../Cellar/python@2/2.7.17_1/bin/python2.7-config
lrwxr-xr-x  1 xxx  admin  40  5 18 10:19 /usr/local/bin/python3 -> ../Cellar/[email protected]/3.9.1_8/bin/python3
lrwxr-xr-x  1 xxx  admin  47  5 18 10:19 /usr/local/bin/python3-config -> ../Cellar/[email protected]/3.9.1_8/bin/python3-config
lrwxr-xr-x  1 xxx  admin  40  1 14 18:06 /usr/local/bin/python3.8 -> ../Cellar/[email protected]/3.8.5/bin/python3.8
lrwxr-xr-x  1 xxx  admin  47  1 14 18:06 /usr/local/bin/python3.8-config -> ../Cellar/[email protected]/3.8.5/bin/python3.8-config
lrwxr-xr-x  1 xxx  admin  42  5 18 10:19 /usr/local/bin/python3.9 -> ../Cellar/[email protected]/3.9.1_8/bin/python3.9
lrwxr-xr-x  1 xxx  admin  49  5 18 10:19 /usr/local/bin/python3.9-config -> ../Cellar/[email protected]/3.9.1_8/bin/python3.9-config
lrwxr-xr-x  1 xxx  admin  39  5 18 17:03 /usr/local/bin/pythonw -> ../Cellar/python@2/2.7.17_1/bin/pythonw
lrwxr-xr-x  1 xxx  admin  40  5 18 17:03 /usr/local/bin/pythonw2 -> ../Cellar/python@2/2.7.17_1/bin/pythonw2
lrwxr-xr-x  1 xxx  admin  42  5 18 17:03 /usr/local/bin/pythonw2.7 -> ../Cellar/python@2/2.7.17_1/bin/pythonw2.7

 

五. 参考

1. https://brew.sh/index_zh-cn
2. https://docs.brew.sh/
3. https://docs.brew.sh/Homebrew-and-Python
4. https://docs.brew.sh/Deprecating-Disabling-and-Removing-Formulae
5. https://devguide.python.org/#status-of-python-branches
6. https://pip.readthedocs.io/en/stable/installing/#install-pip
7. https://www.python.org/downloads/
8. https://www.python.org/dev/peps/pep-0373/
9. https://github.com/Homebrew/brew
10. https://github.com/Homebrew/brew/issues/7057
11. https://github.com/Homebrew/homebrew-core/issues/50546
12. https://github.com/Homebrew/brew/pull/7066
13. https://github.com/Homebrew/brew/pull/7019
14. https://github.com/Homebrew/homebrew-core/pull/49796
15. https://stackoverflow.com/questions/tagged/python-2.7
16. https://stackoverflow.com/questions/60298514/how-to-reinstall-python2-from-homebrew

 

 

 

(完)