When developing Python applications, the system has only one version of Python 3 installed: 3.x. All third-party packages will be installed by pip in the site packages directory of Python 3.
If we want to develop multiple applications at the same time, these applications will share the same python, which is Python 3 installed on the system. What if application A needs Python 2.7 and application B needs Python 3?
In this case, each application may need to have its own "independent" Python running environment. virtualenv is used to create a set of "isolated" Python running environment for an application.
1, virtualenvwrapper
virtualenvwrapper is an extension package of virtualenv, which is used for more convenient management of virtual environment. You can:
- Consolidate all virtual environments in one directory
- Unified management of virtual environment
- Fast switch virtual environment
1. Installation
Windows PIP installation:
C:\Users\Rnanprince>pip install virtualenvwrapper-win Collecting virtualenvwrapper-win Downloading virtualenvwrapper-win-1.2.6.tar.gz (21 kB) Collecting virtualenv Using cached virtualenv-20.0.25-py2.py3-none-any.whl (4.7 MB) ... Successfully built virtualenvwrapper-win Installing collected packages: virtualenv, virtualenvwrapper-win Successfully installed virtualenv-20.0.25 virtualenvwrapper-win-1.2.6
Linux apt and pip installation
apt Installation: $ sudo apt-get install virtualenvwrapper pip Installation: $ sudo pip install virtualenvwrapper $ sudo echo "source virtualenvwrapper.sh">>~/.bashrc
2. View version
C:\Users\Rnanprince>virtualenv --version virtualenv 20.0.25 from d:\program files\anaconda3\lib\site-packages\virtualenv\__init__.py ERROR:root:SystemExit: 0
3. Create a running environment
C:\Users\Rnanprince>mkvirtualenv --python=python3 venv3
created virtual environment CPython3.7.3.final.0-64 in 4898ms
creator CPython3Windows(dest=C:\Users\Rnanprince\Envs\venv3, clear=False, global=False)
seeder FromAppData(download=False, pip=bundle, setuptools=bundle, wheel=bundle, via=copy, app_data_dir=C:\Users\Rnanprince\AppData\Local\pypa\virtualenv)
added seed packages: pip==20.1.1, setuptools==47.3.1, wheel==0.34.2
activators BashActivator,BatchActivator,FishActivator,PowerShellActivator,PythonActivator,XonshActivator4. List virtual environments
(venv) C:\Users\Rnanprince>lsvirtualenv //or (venv) C:\Users\Rnanprince>workon Pass a name to activate one of the following virtualenvs: ============================================================================== venv2 venv3
5. Activate - switch environment
(venv3) C:\Users\Rnanprince>workon venv2 (venv2) C:\Users\Rnanprince>
6. Exit environment
(venv2) C:\Users\Rnanprince>deactivate C:\Users\Rnanprince>
7. Delete environment
(venv3) C:\Users\Rnanprince>rmvirtualenv venv
Deleted C:\Users\Rnanprince\Envs\venv8. Other parameters:
- add2virtualenv: add directory to the import path
- cdproject: change directory to the active project
- cdsitepackages: change to the site-packages directory
- cdvirtualenv: change to the $VIRTUAL_ENV directory
- lssitepackages: list contents of the site-packages directory
- lsvirtualenv: list virtualenvs
- mkproject: create a new project directory and its associated virtualenv
- mkvirtualenv: Create a new virtualenv in $WORKON_HOME
- rmvirtualenv: Remove a virtualenv
- setprojectdir: associate a project directory with a virtualenv
- toggleglobalsitepackages: turn access to global site-packages on/off
- virtualenvwrapper: show this help message
- whereis: return full path to executable on path.
- workon: list or change working virtualenvs
2, Using conda management
conda can directly create virtual environments of different Python versions. virtualenv only specifies the virtual environment of different versions of python, provided that you have installed different versions of python, which is not flexible compared with conda.
1. Installation
Download the python of anaconda and use the conda tool directly.
To view the conda version:
C:\Users\Rnanprince>conda --version conda 4.8.3
Update conda version:
C:\Users\Rnanprince>pip install --upgrade conda
2. Create a virtual environment
Create different python versions, write out the version number directly, and install the desired libraries at the same time.
C:\Users\Rnanprince>conda create -n venv2 python=2.7 C:\Users\Rnanprince>conda create -n venv2 python=3.6
The following NEW packages will be INSTALLED: ca-certificates pkgs/main/win-64::ca-certificates-2020.1.1-0 certifi pkgs/main/win-64::certifi-2020.6.20-py37_0 openssl pkgs/main/win-64::openssl-1.1.1g-he774522_0 pip pkgs/main/win-64::pip-20.1.1-py37_1 python pkgs/main/win-64::python-3.7.7-h81c818b_4 setuptools pkgs/main/win-64::setuptools-47.3.1-py37_0 sqlite pkgs/main/win-64::sqlite-3.32.3-h2a8f88b_0 vc pkgs/main/win-64::vc-14.1-h0510ff6_4 vs2015_runtime pkgs/main/win-64::vs2015_runtime-14.16.27012-hf0eaf9b_2 wheel pkgs/main/win-64::wheel-0.34.2-py37_0 wincertstore pkgs/main/win-64::wincertstore-0.2-py37_0 zlib pkgs/main/win-64::zlib-1.2.11-h62dcd97_4
3. List virtual environments
C:\Users\Rnanprince>conda info -e //Or: C:\Users\Rnanprince>conda env list # conda environments: # base * D:\Program Files\Anaconda3 venv2 D:\Program Files\Anaconda3\envs\venv2 venv3 D:\Program Files\Anaconda3\envs\venv3
4. Activate virtual environment
windows: C:\Users\Rnanprince>activate venv2 Linux: source activate venv2
5. Exit virtual environment
windows: (venv2) C:\Users\Rnanprince>conda deactivate Linux: source conda deactivate
6. Delete virtual environment
C:\Users\Rnanprince>conda remove --name venv --all
7. View installation package
Current environment:
(venv2) C:\Users\Rnanprince>conda list # packages in environment at D:\Program Files\Anaconda3\envs\venv2: # # Name Version Build Channel ca-certificates 2020.1.1 0 certifi 2019.11.28 py27_0 pip 19.3.1 py27_0 python 2.7.18 hfb89ab9_0 setuptools 44.0.0 py27_0 sqlite 3.30.1 h0c8e037_0 vc 9 h7299396_1 vs2008_runtime 9.00.30729.1 hfaea7d5_1 wheel 0.33.6 py27_0 wincertstore 0.2 py27hf04cefb_0
A specified environment:
C:\Users\Rnanprince>conda list -n venv2 # packages in environment at D:\Program Files\Anaconda3\envs\venv2: # # Name Version Build Channel ca-certificates 2020.1.1 0 certifi 2019.11.28 py27_0 pip 19.3.1 py27_0 python 2.7.18 hfb89ab9_0 setuptools 44.0.0 py27_0 sqlite 3.30.1 h0c8e037_0 vc 9 h7299396_1 vs2008_runtime 9.00.30729.1 hfaea7d5_1 wheel 0.33.6 py27_0 wincertstore 0.2 py27hf04cefb_0
8. Installation package processing
Installation:
C:\Users\Rnanprince>conda install -n venv2 numpy C:\Users\Rnanprince>conda list -n venv2
to update:
C:\Users\Rnanprince>conda update -n venv2 numpy
Delete:
C:\Users\Rnanprince>conda remove -n venv2 numpy C:\Users\Rnanprince>conda list -n venv2 # packages in environment at D:\Program Files\Anaconda3\envs\venv2: # # Name Version Build Channel ca-certificates 2020.1.1 0 certifi 2019.11.28 py27_0 pip 19.3.1 py27_0 python 2.7.18 hfb89ab9_0 setuptools 44.0.0 py27_0 sqlite 3.30.1 h0c8e037_0 vc 9 h7299396_1 vs2008_runtime 9.00.30729.1 hfaea7d5_1 wheel 0.33.6 py27_0 wincertstore 0.2 py27hf04cefb_0