环境： macOS big sur， zsh

pip install virtualenv

安装后提示：

WARNING: The script virtualenv is installed in '/Users/tonyyan/Library/Python/2.7/bin' which is not on PATH.
  Consider adding this directory to PATH or, if you prefer to suppress this warning, use --no-warn-script-location.

为zsh添加环境变量：

vi ~/.zshrc

加入以下两行：

# virtualenv for python2.7
export PATH="$PATH:/Users/tonyyan/Library/Python/2.7/bin"

保存并退出vim

source ~/.zshrc

此时可以验证 virtualenv已成功安装

virtualenv --version 

virtualenv 20.7.2 from /Users/tonyyan/Library/Python/2.7/lib/python/site-packages/virtualenv/__init__.pyc