Turn: Use virtualenv to build a separate Python environment

Turn from: http://qicheng0211.blog.51cto.com/3958621/1561685 Thank you for the hard work of the author

Virtualenv can build a virtual and stand-alone Python environment, allowing each project environment to be isolated from other projects, keeping the environment clean, and resolving package conflict issues.

First, install the virtualenv

Virtualenv is actually a python package, so we can install it with Easy_install or PIP. The installation methods on the CentOS system are described below.

Easy_install Installation Method:

12	[[email protected] ~]# yum install python-setuptools python-devel[[email protected] ~]# easy_install virtualenv

Pip installation Method:

12	[[email protected] ~]# easy_install pip[[email protected] ~]# pip install virtualenv

Yum installation mode (Epel source):

1	[[email protected] ~]# yum install python-virtualenv

Ii. Creating a Python virtual environment

Create a Python virtual environment using the VIRTUALENV command: virtualenv [virtual Environment name].

123	[[email protected] ~]# virtualenv env1New python executable inenv1/bin/pythonInstalling setuptools, pip...done.

Once executed, a folder with the same name as the virtual environment is generated locally.

If you have different versions of Python installed in your system, you can use the--python parameter to specify the Python version of the virtual environment:

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[[email protected] ~]# virtualenv --python=/usr/local/python-2.7.8/bin/python2.7 env1Running virtualenv with interpreter /usr/local/python-2.7.8/bin/python2.7New python executable inenv1/bin/python2.7Also creating executable inenv1/bin/pythonInstalling setuptools, pip...done.

Measured by default, the virtual environment does not rely on the global site-packages of the system environment. For example, the system environment installed MYSQLDB module, in the virtual environment import MySQLdb will prompt importerror. If you want to rely on a third-party package for your system environment, you can use parameter--system-site-packages. Alternatively, you can use the Virtualenvwrapper toggleglobalsitepackages command to control whether the current environment uses global site-packages.

123	[[email protected] ~]# virtualenv --system-site-packages env1New python executable inenv1/bin/pythonInstalling setuptools, pip...done.

Third, start the virtual environment

Enter the virtual environment directory and start the virtual environment as follows:

1234	[[email protected] ~]# cd env1/[[email protected] env1]# source bin/activate(env1)[[email protected] env1]# python -VPython 2.7.8

At this point the command line will be preceded by a parenthesis with the name of the virtual environment in parentheses. All modules installed later Easy_install or PIP will be installed in the virtual environment directory.

Iv. exiting the virtual environment

Exiting the virtual environment: deactivate

12	(env1)[[email protected] env1]# deactivate[[email protected] env1]#

V. Use of Virtualenvwrapper

Virtualenvwrapper is a virtualenv extension tool that makes it easy to create, delete, copy, and switch between different virtual environments.

1. Installing Virtualenvwrapper

1	[[email protected] ~]# easy_install virtualenvwrapper

Or:

1	[[email protected] ~]# pip install virtualenvwrapper

Create a folder to hold all the virtual environments:

1	[[email protected] ~]# mkdir ~/workspaces

Set the environment variable and add the following two lines to the ~/.BASHRC.

12	[[email protected] ~]# export WORKON_HOME=~/workspaces[[email protected] ~]# source /usr/bin/virtualenvwrapper.sh

Then you can use the Virtualenvwrapper.
2. Create a virtual Environment: mkvirtualenv [Virtual Environment name]

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[[email protected] ~]# mkvirtualenv env1New python executable inenv1/bin/pythonInstalling setuptools, pip...done.(env1)[[email protected] ~]# mkvirtualenv env2New python executable inenv2/bin/pythonInstalling setuptools, pip...done.(env2)[[email protected] ~]#

Note: mkvirtualenv can use virtualenv parameters, such as--python, to specify the Python version. Once the virtual environment is created, it is automatically switched to this virtual environment. The virtual Environment directory is in Workon_home.

3. List Virtual environments: Lsvirtualenv-b

123	(env2)[[email protected] ~]# lsvirtualenv -benv1env2

4. Switch virtual Environment: Workon [Virtual Environment name]

123	(env2)[[email protected] ~]# workon env1(env1)[[email protected] ~]# echo $VIRTUAL_ENV/root/workspaces/env1

5. Check which packages are installed in the environment: lssitepackages

6. Enter the current environment directory: cdvirtualenv [subdirectory name]

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(env1)[[email protected] ~]# cdvirtualenv(env1)[[email protected] env1]# pwd/root/workspaces/env1(env1)[[email protected] env1]# cdvirtualenv bin(env1)[[email protected] bin]# pwd/root/workspaces/env1/bin

Enter the Site-packages directory for the current environment: cdsitepackages [subdirectory name]

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< Code class= "Bash plain" > (ENV1) [[EMAIL&NBSP;PROTECTED]&NBSP;ENV1] #  Cdsitepackages (ENV1) [[Email protected] site-packages] # pwd /root/workspaces/env1/lib/python2 .6 /site-packages (ENV1) [[ Email protected] site-packages] # cdsitepackages pip (ENV1) [[Email protected] pip] #  pwd /root/workspaces/env1/lib/python2 .6 /site-packages/pip

7. Control whether the environment uses global site-packages:toggleglobalsitepackages

8. Replicating the Virtual environment: cpvirtualenv [Source] [dest]

123	[[email protected] ~]# cpvirtualenv env1 env3Copying env1 as env3...(env3)[[email protected] ~]#

9. Exit the virtual environment: deactivate

10. Delete Virtual Environment: rmvirtualenv [Virtual Environment name]

12	[[email protected] ~]# rmvirtualenv env2Removing env2...

Turn: Use virtualenv to build a separate Python environment