pip 安装失败并显示 ImportError: cannot import name 'SourceDistribution'

Question

在干净的 venv 中安装某些东西的示例：

$ rm -rf venv && python3.8 -m venv venv && ./venv/bin/python -m pip install -U pip && ./venv/bin/python -m pip install requests
Collecting pip
  Using cached https://files.pythonhosted.org/packages/60/65/16487a7c4e0f95bb3fc89c2e377be331fd496b7a9b08fd3077de7f3ae2cf/pip-20.0-py2.py3-none-any.whl
Installing collected packages: pip
  Found existing installation: pip 19.2.3
    Uninstalling pip-19.2.3:
      Successfully uninstalled pip-19.2.3
Successfully installed pip-20.0
Traceback (most recent call last):
  File "/opt/local/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/runpy.py", line 193, in _run_module_as_main
    return _run_code(code, main_globals, None,
  ...
  File "/Users/messa/test/venv/lib/python3.8/site-packages/pip/_internal/distributions/__init__.py", line 1, in <module>
    from pip._internal.distributions.source import SourceDistribution
ImportError: cannot import name 'SourceDistribution' from 'pip._internal.distributions.source' (/Users/messa/test/venv/lib/python3.8/site-packages/pip/_internal/distributions/source/__init__.py)

Answer 1

当前 pip 版本 20.0 已损坏 - 请参阅https://github.com/pypa/pip/issues/7620

安装 20.0 以外的 pip：

$ pip install -U "pip!=20.0"

更新： pip 20.0.1 已发布，修复了此问题。

如果您被20.0卡住并且由于此错误而无法升级到 20.0.1，请尝试get-pip.py或easy_install。

$ curl https://bootstrap.pypa.io/get-pip.py -o get-pip.py
$ python get-pip.py --ignore-installed