pip3启动报错：找不到pip==20.0.2依赖的解决求助

环境信息 #

我的Python版本：

python --version
Python 2.7.18
python3 --version
Python 3.10.0

通过sudo apt-get install python3-pip安装pip3后，执行pip3命令出现以下报错：

$ pip3
Traceback (most recent call last):
  File "/usr/local/lib/python3.10/site-packages/pkg_resources/__init__.py", line 568, in _build_master
    ws.require(__requires__)
  File "/usr/local/lib/python3.10/site-packages/pkg_resources/__init__.py", line 886, in require
    needed = self.resolve(parse_requirements(requirements))
  File "/usr/local/lib/python3.10/site-packages/pkg_resources/__init__.py", line 777, in resolve
    raise VersionConflict(dist, req).with_context(dependent_req)
pkg_resources.VersionConflict: (pip 21.2.3 (/usr/local/lib/python3.10/site-packages), Requirement.parse('pip==20.0.2'))

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/usr/bin/pip3", line 6, in <module>
    from pkg_resources import load_entry_point
  File "/usr/local/lib/python3.10/site-packages/pkg_resources/__init__.py", line 3243, in <module>
    def _initialize_master_working_set():
  File "/usr/local/lib/python3.10/site-packages/pkg_resources/__init__.py", line 3226, in _call_aside
    f(*args, **kwargs)
  File "/usr/local/lib/python3.10/site-packages/pkg_resources/__init__.py", line 3255, in _initialize_master_working_set
    working_set = WorkingSet._build_master()
  File "/usr/local/lib/python3.10/site-packages/pkg_resources/__init__.py", line 570, in _build_master
    return cls._build_from_requirements(__requires__)
  File "/usr/local/lib/python3.10/site-packages/pkg_resources/__init__.py", line 583, in _build_from_requirements
    dists = ws.resolve(reqs, Environment())
  File "/usr/local/lib/python3.10/site-packages/pkg_resources/__init__.py", line 772, in resolve
    raise DistributionNotFound(req, requirers)
pkg_resources.DistributionNotFound: The 'pip==20.0.2' distribution was not found and is required by the application

解决思路 #

• 彻底清理现有pip3：
  执行sudo apt-get purge python3-pip移除apt安装的pip3，再删除残留的pip文件：sudo rm -rf /usr/local/lib/python3.10/site-packages/pip*
• 用Python内置工具重新安装适配版本的pip：
  运行python3 -m ensurepip --upgrade，这个命令会为当前Python3.10安装匹配的pip版本，从根源避免版本冲突
• 验证修复：
  执行pip3 --version，若正常显示版本信息则问题解决
• 备选方案（若ensurepip不可用）：
  下载官方安装脚本：curl https://bootstrap.pypa.io/get-pip.py -o get-pip.py，然后强制重新安装：python3 get-pip.py --force-reinstall

内容的提问来源于stack exchange，提问作者stevezkw