錯誤：module 'pip' has no attribute 'main'

pip升級到10.0.1之后可能會出現這個錯誤。

環境：
pip version : 10.0.1
python version : 3.6.4
mac os : 10.12.6 

錯誤出現路徑還原：

升級pip
$python -m pip install pip --upgrade
Requirement already up-to-date: pip in /usr/local/lib/python3.6/site-packages (10.0.1)

升級后使用pip，報錯
$pip -V
Traceback (most recent call last):
  File "/usr/local/lib/python3.6/site-packages/pkg_resources/__init__.py", line 2332, in resolve
    return functools.reduce(getattr, self.attrs, module)
AttributeError: module 'pip' has no attribute 'main'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/usr/local/opt/python/libexec/bin/pip", line 11, in <module>
    load_entry_point('pip==9.0.3', 'console_scripts', 'pip3')()
  File "/usr/local/lib/python3.6/site-packages/pkg_resources/__init__.py", line 480, in load_entry_point
    return get_distribution(dist).load_entry_point(group, name)
  File "/usr/local/lib/python3.6/site-packages/pkg_resources/__init__.py", line 2693, in load_entry_point
    return ep.load()
  File "/usr/local/lib/python3.6/site-packages/pkg_resources/__init__.py", line 2324, in load
    return self.resolve()
  File "/usr/local/lib/python3.6/site-packages/pkg_resources/__init__.py", line 2334, in resolve
    raise ImportError(str(exc))
ImportError: module 'pip' has no attribute 'main'

解決方法：

• 方法一（未測試）
  網上有類似的錯誤描述：stackoverflow這里
  里邊提到降級處理：

python3 -m pip install --user --upgrade pip==9.0.3

沒有親測這種方式，應該是可以的。

• 方法二（已測試，有效）
  更新pip

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

其中，如果是python3對應的pip3，則需要使用python3，如下：

$python3 get-pip.py

更新完畢，便可使用pip或者pip3

$pip -V
pip 10.0.1 from /usr/local/lib/python3.6/site-packages/pip (python 3.6)
$pip3 -V
pip 10.0.1 from /usr/local/lib/python3.6/site-packages/pip (python 3.6)

• 方法三（未測試）
  網上有說重新安裝python3即可解決，這里，未測試。

brew reinstall python3

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