error code:

Traceback (most recent call last): 
  File "/usr/bin/pip", line 7, in <module>
  from pip._internal import main
ModuleNotFoundError: No module named 'pip._internal'

Solution: upgrading Python 2.7.5 of centos7 to Python 3.6,
I compiled and installed it, and when I installed it, I prompted that PIP was successfully installed,
because there was an incompatible version in the resolved dependency
if you upgrade to Python 3.7.2, it will be even more strange. The SSL module won’t work

Solution: there are two ways, one is to install and the other is to upgrade, which are just two commands
installed: 1: WGet https://bootstrap.pypa.io/get-pip.py –No check certificate
2: sudo Python get-pip.Py
upgraded: 1: PIP install — user — upgrade pipenv
2: Python – M PIP install — upgrade pip