virtualenv create a python virtual environment

Why create a virtual environment python

In the development of Python applications, system installation Python3 only one version: 3.4. All third-party packages will be pipinstalled to Python3 the site-packagesdirectory.

If we want to develop multiple applications simultaneously, and that these applications will share a Python, it is installed in the system's Python 3. If the application A needs jinja 2.7, while application B needs jinja 2.6 how to do?

In this case, each application may need to have their own set of "independence" of the Python runtime environment. virtualenv is used to create a "quarantine" of the Python runtime environment for an application.

 

Create a virtual environment

Installation virtualenv

pip install virtualenv

 

Create a virtual environment

1 Create a directory to store all virtual environments 
virtualenv_all 

2 to create a virtual environment, generally named after the project. 
Cd virtualenv_all 
virtualenv s22_crm 

# create success can be seen more than a directory, is to copy a python interpreter 
ccdeMacBook - Air: LS CC $ virtualenv_all 
s22_crm 
ccdeMacBook -Air: virtualenv_all CC $ LS s22_crm / 
bin the include lib 

3 . enter the virtual environment 
ccdeMacBook -Air: virtualenv_all s22_crm CC $ cd / 
ccdeMacBook -Air: s22_crm CC $ Source bin / of an activate 
(s22_crm) ccdeMacBook - Air : s22_crm CC $ 

# Python environment variable to point to the virtual environment has been very clean, had nothing. You can install all dependencies needed project in a virtual environment. 
(s22_crm) ccdeMacBook -Air:s22_crm cc$ pip list
Package    Version
---------- -------
pip        20.0.2 
setuptools 46.1.3 
wheel      0.34.2 
(s22_crm) ccdeMacBook-Air:s22_crm cc$ which pip
/Users/xiaochao/Documents/code/python_s22/virtualenv_all/s22_crm/bin/pip

(s22_crm) ccdeMacBook-Air:s22_crm cc$ which python
/Users/xiaochao/Documents/code/python_s22/virtualenv_all/s22_crm/bin/python

4. 退出虚拟环境
(s22_crm) ccdeMacBook-Air:s22_crm cc$ deactivate 
ccdeMacBook-Air:s22_crm cc$ 

 

PyCharm using a virtual environment 

 

 

 

PyCharm create a virtual environment