1. What is a virtual environment
A set of development environments virtualized based on the large environment of Python . Virtual environments are independent of each other. Packages installed in a virtual environment do not affect the real python environment or other virtual environments.
2. Install VirtualEnv
sudo pip3 install virtualenv
3. Create and use virtual environments
1. Preparation
mkdir MyEnv
cd MyEnv
2. Create a virtual environment
virtualenv virtual environment name
ex:
virtualenv default
Create a virtual environment with the specified version
virtualenv -p /usr/bin/python2.7 name
virtualenv -p /usr/bin/python3.5 name
Note: You cannot use sudo authorization when using pip to install python packages in a virtual environment , otherwise, it will be installed in the real python environment
3. Start the virtual environment
bin/activate in the virtual environment directory
Execute activate to start the virtual environment
Note: You cannot start a virtual environment in the bin directory
source bin/activate
4. Exit the virtual environment
deactivate
5. Delete the virtual environment
rm virtual environment directory -rf
3. Python tool - VirtualEnvWrapper ( virtual environment management tool )
1. Function
A third-party virtual environment management tool that can quickly, efficiently and conveniently manage virtual environments
2. Install virtual environment management tools
sudo pip3 install virtualenvwrapper
3. Configure virtualenvwrapper
In the ~ directory, there is a terminal management file .bashrc ( enter ll in the ~ directory)
Modify .bashrc : sudo vi .bashrc
在.bashrc 最底部增加以下内容：
1、export WORKON_HOME=~/MyEnv
将~/MyEnv作为虚拟环境管理目录，所有使用virtualenvwrapper创建的虚拟环境默认都保存于此
2、如果系统中包含多个python环境的话，则必须增加以下内容
export VIRTUALENVWRAPPER_PYTHON=/usr/bin/python3
3、source /usr/local/bin/virtualenvwrapper.sh
4、在 ~ 目录下，执行一遍 .bashrc
source .bashrc
4、使用虚拟环境管理工具
1、创建并进入到虚拟环境
1、mkvirtualenv 虚拟环境名称
2、mkvirtualenv --python=/usr/bin/python2.7 虚拟环境名称
2、查询当前所维护的所有虚拟环境
workon
3、切换虚拟环境
workon 虚拟环境名称
4、退出虚拟环境
deactivate
5、删除虚拟环境
rmvirtualenv 虚拟环境名称