Python3.11执行pip安装时email模块元数据生成失败求助

问题场景 #

执行pip install -r win_requirements.txt时，因尝试安装email模块触发错误，直接执行pip3 install email也会出现如下报错：

pip3 install email
Defaulting to user installation because normal site-packages is not writeable
Collecting email
  Using cached email-4.0.2.tar.gz (1.2 MB)
  Preparing metadata (setup.py) ... error
  error: subprocess-exited-with-error
  
  × python setup.py egg_info did not run successfully.
  │ exit code: 1
  ╰─> [18 lines of output]
      Traceback (most recent call last):
        File "<string>", line 2, in <module>
        File "<pip-setuptools-caller>", line 14, in <module>
        File "/usr/lib/python3/dist-packages/setuptools/__init__.py", line 15, in <module>
          import setuptools.version
        File "/usr/lib/python3/dist-packages/setuptools/version.py", line 1, in <module>
          from ._importlib import metadata
        File "/usr/lib/python3/dist-packages/setuptools/_importlib.py", line 45, in <module>
          import importlib.metadata as metadata  # noqa: F401
          ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
        File "/usr/lib/python3.11/importlib/metadata/__init__.py", line 17, in <module>
          from . import _adapters, _meta
        File "/usr/lib/python3.11/importlib/metadata/_adapters.py", line 3, in <module>
          import email.message
        File "/tmp/pip-install-lzxy69gd/email_f38b626eeefa44a098244f34710a1052/email/message.py", line 255
          if str(charset) <> charset.get_output_charset():
                          ^^
      SyntaxError: invalid syntax
      [end of output]
  
  note: This error originates from a subprocess, and is likely not a problem with pip.
error: metadata-generation-failed

× Encountered error while generating package metadata.
╰─> See above for output.

note: This is an issue with the package mentioned above, not pip.
hint: See above for details.

问题原因 #

1. email是Python标准库内置模块，无需通过pip安装，直接在代码里import email即可使用。
2. PyPI上的email包（版本4.0.2）是极其老旧的Python 2.x兼容版本，代码中使用了Python 3已废弃的<>不等于运算符（Python 3中统一用!=），因此在Python 3.11环境下触发语法错误。

解决方案 #

• 打开win_requirements.txt，删除其中的email条目，重新执行pip install -r win_requirements.txt。
• 如果代码需要邮箱验证、解析等扩展功能，不要使用这个老旧包，改用现代第三方库，比如email-validator（执行pip install email-validator安装）。

内容的提问来源于stack exchange，提问作者John Smith II