首先安装python和python3

Linux
注意自己电脑python装的路径

which pip
-> /usr/bin/python
which pip3
-> /usr/bin/python3
sudo ln -s /usr/bin/python /usr/bin/python3

如果不行：

sudo update-alternatives --install /usr/bin/python python /usr/bin/python2 1
sudo update-alternatives --install /usr/bin/python python /usr/bin/python3 2

Mac

which pip
-> path_pip
which pip3
-> path_pip3
sudo ln -s path_pip path_pip3

如果不行，shift+alt+.，打开目录下的
在文件中输入以下内容：【注意path，用which命令去查查！】

#Setting PATH for Python 3.7
#The original version is saved in .bash_profile.pysave
PATH="/usr/local/Cellar/python/3.7.0/bin:${PATH}"
export PATH
alias python="/usr/local/bin/python3"

# Setting PATH for pip 3.7
export PATH="/Library/Frameworks/Python.framework/Versions/3.7/bin:$PATH"

保存之后：

source ~/.bash_profile

#检查
python -V
pip -V