Traceback (most recent call last): File "/usr/bin/pip3", line 9, in <module> from pip impor...

pip install -i https://pypi.tuna.tsinghua.edu.cn/simple pip -U
pip config set global.index-url https://pypi.tuna.tsinghua.edu.cn/simple

Traceback (most recent call last):
  File "/usr/bin/pip3", line 9, in <module>
    from pip import main
ImportError: cannot import name 'main'

sudo /usr/bin/pip3

from pip import main
if __name__ == '__main__':
    sys.exit(main())

from pip import __main__
if __name__ == '__main__':
    sys.exit(__main__._main())