Python Virtual Environment virtualenv

virtualenv is used to create multiple standalone Python runtime environments on a single machine, which resolves:

1. Third-party package dependencies between quarantined items

2. Install a new Python package without permission

In addition, there is an additional benefit: when deploying an application, package the virtual environment of the development environment into a production environment.

1. Installation

C:\python27>pip Install Virtualenv

1. Role

D:\mysite>c:\python27\scripts\virtualenv.exe env_py27

The above code installs the ENV_PY27 environment directory in the D:\mysite directory with its file structure:

Directory of D:\mysite\env_py272018/ to/ -   .: .<DIR>          .2018/ to/ -   .: .<DIR>          ..2018/ to/ -   .: .<DIR>Include2018/ to/ -   .: .<DIR>Lib2018/ to/ -   .: .<DIR> Scripts

Where lib/site-packages contains the libraries that are installed from the system under PYTHON27. By default, the virtual environment relies on site packages in the system environment, which means that the third-party package that is already installed in the system is installed in the virtual environment, and if you do not want to rely on the package, you can add parameters- No-site-packages setting up a virtual environment

Virtualenv--no-site---no-site-packages env_py27

3. Enabling the Virtual environment

D:\mysite\env_py27>scripts\activate

4. Deactivate a virtual environment

D:\mysite\env_py27>scripts\deactivate

Python Virtual Environment virtualenv