pip从9.0.1升级到20.2.4不可用

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背景介绍：

系统提示我升级pip，我就把它升级了：

You are using pip version 9.0.1, however version 20.2.4 is available.
You should consider upgrading via the 'pip install --upgrade pip' command

我就使用命令升级：

pip install --upgrade pip

结果升级之后发现pip -V 报了这么一大堆错：

[root@localhost ~]# pip -V
Traceback (most recent call last):
  File "/usr/python3.6/lib/python3.6/site-packages/pkg_resources/__init__.py", line 659, in _build_master
    ws.require(__requires__)
  File "/usr/python3.6/lib/python3.6/site-packages/pkg_resources/__init__.py", line 967, in require
    needed = self.resolve(parse_requirements(requirements))
  File "/usr/python3.6/lib/python3.6/site-packages/pkg_resources/__init__.py", line 858, in resolve
    raise VersionConflict(dist, req).with_context(dependent_req)
pkg_resources.VersionConflict: (pip 20.2.4 (/usr/python3.6/lib/python3.6/site-packages), Requirement.parse('pip==9.0.1'))

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/usr/bin/pip", line 5, in <module>
    from pkg_resources import load_entry_point
  File "/usr/python3.6/lib/python3.6/site-packages/pkg_resources/__init__.py", line 3017, in <module>
    @_call_aside
  File "/usr/python3.6/lib/python3.6/site-packages/pkg_resources/__init__.py", line 3003, in _call_aside
    f(*args, **kwargs)
  File "/usr/python3.6/lib/python3.6/site-packages/pkg_resources/__init__.py", line 3030, in _initialize_master_working_set
    working_set = WorkingSet._build_master()
  File "/usr/python3.6/lib/python3.6/site-packages/pkg_resources/__init__.py", line 661, in _build_master
    return cls._build_from_requirements(__requires__)
  File "/usr/python3.6/lib/python3.6/site-packages/pkg_resources/__init__.py", line 674, in _build_from_requirements
    dists = ws.resolve(reqs, Environment())
  File "/usr/python3.6/lib/python3.6/site-packages/pkg_resources/__init__.py", line 853, in resolve
    raise DistributionNotFound(req, requirers)
pkg_resources.DistributionNotFound: The 'pip==9.0.1' distribution was not found and is required by the application

经过多次尝试，这个方法成功了：

 

原来是版本信息需要自己手动更新
[root@localhost bin]# pwd
/usr/bin
[root@localhost bin]# vim pip

#!/usr/bin/python
# EASY-INSTALL-ENTRY-SCRIPT: 'pip==9.0.1','console_scripts','pip'
__requires__ = 'pip==20.2.4'
import sys
from pkg_resources import load_entry_point

if __name__ == '__main__':
    sys.exit(
        load_entry_point('pip==20.2.4', 'console_scripts', 'pip')()
    )
~                                                                     


[root@localhost bin]# pip -V
pip 20.2.4 from /usr/python3.6/lib/python3.6/site-packages/pip (python 3.6)

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