Python Virtual Environment: Difference between revisions

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Load one of the Python modules available on Cheaha in your environment.
Load one of the Python modules available on Cheaha in your environment.
<pre>
<pre>
[ravi89@login001 ~]$ module avail Python
[snoopy@c1 ~]$ module avail Python


-------------------------- /share/apps/rc/modules/all --------------------------
-------------------------- /share/apps/rc/modules/all --------------------------
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Once you have loaded Python, we would use '''virtualenv''' to create and manage virtual environments.
Once you have loaded Python, we would use '''virtualenv''' to create and manage virtual environments.
<pre>
<pre>
[ravi89@login001 Python_Environments]$ module load Python/3.6.3-intel-2017a  
[snoopy@c1 Python_Environments]$ module load Python/3.6.3-intel-2017a  
[ravi89@login001 Python_Environments]$ virtualenv test_environment
[snoopy@c1 Python_Environments]$ virtualenv test_environment
Using base prefix '/share/apps/rc/software/Python/3.6.3-intel-2017a'
Using base prefix '/share/apps/rc/software/Python/3.6.3-intel-2017a'
New python executable in /data/user/ravi89/Python_Environments/test_environment/bin/python
New python executable in /data/user/snoopy/Python_Environments/test_environment/bin/python
Installing setuptools, pip, wheel...done.
Installing setuptools, pip, wheel...done.
[ravi89@login001 Python_Environments]$
[snoopy@c1 Python_Environments]$
</pre>
</pre>


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Once a virtual environment has been created, you need to activate it to be in the virtual environment.
Once a virtual environment has been created, you need to activate it to be in the virtual environment.
<pre>
<pre>
[ravi89@login001 Python_Environments]$ source test_environment/bin/activate
[snoopy@c1 Python_Environments]$ source test_environment/bin/activate
(test_environment) [ravi89@login001 Python_Environments]$
(test_environment) [snoopy@c1 Python_Environments]$
</pre>
</pre>
Activating the virtual environment will change your shell’s prompt to show what virtual environment you’re using, test_environment in the above case, and modify the environment so that you can install Python packages in the environment.
Activating the virtual environment will change your shell’s prompt to show what virtual environment you’re using, test_environment in the above case, and modify the environment so that you can install Python packages for that particular environment.


===Maintaining a Virtual Environment===
===Maintaining a Virtual Environment===
After this you can install the packages that you would like for this environment, using '''pip'''. [https://pip.pypa.io/en/stable/ pip] is a package management system used to install and manage software packages written in Python.
After this you can install the packages that you would like for this environment, using '''pip'''. [https://pip.pypa.io/en/stable/ pip] is a package management system used to install and manage software packages written in Python.
<pre>
<pre>
(test_environment) [ravi89@login001 Python_Environments]$ pip install numpy
(test_environment) [snoopy@c1 Python_Environments]$ pip install numpy
Collecting numpy
Collecting numpy
   Downloading numpy-1.14.0-cp36-cp36m-manylinux1_x86_64.whl (17.2MB)
   Downloading numpy-1.14.0-cp36-cp36m-manylinux1_x86_64.whl (17.2MB)
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Installing collected packages: numpy
Installing collected packages: numpy
Successfully installed numpy-1.14.0
Successfully installed numpy-1.14.0
(test_environment) [ravi89@login001 Python_Environments]$ ls test_environment/lib/python3.6/site-packages/
(test_environment) [snoopy@c1 Python_Environments]$ ls test_environment/lib/python3.6/site-packages/
easy_install.py        pip-9.0.1.dist-info  setuptools-38.4.0.dist-info
easy_install.py        pip-9.0.1.dist-info  setuptools-38.4.0.dist-info
numpy                  pkg_resources        wheel
numpy                  pkg_resources        wheel
numpy-1.14.0.dist-info  __pycache__          wheel-0.30.0.dist-info
numpy-1.14.0.dist-info  __pycache__          wheel-0.30.0.dist-info
pip                    setuptools
pip                    setuptools
(test_environment) [ravi89@login001 Python_Environments]$
(test_environment) [snoopy@c1 Python_Environments]$
</pre>
</pre>


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After you are done using the virtual environment, you can use '''deactivate''' command to go back to your bash shell environemnt.
After you are done using the virtual environment, you can use '''deactivate''' command to go back to your bash shell environemnt.
<pre>
<pre>
(test_environment) [ravi89@login001 Python_Environments]$ deactivate  
(test_environment) [snoopy@c1 Python_Environments]$ deactivate  
[ravi89@login001 Python_Environments]$
[snoopy@c1 Python_Environments]$
</pre>
</pre>
It would change your shell's prompt and remove the name of the virtual environment that you were in.
It would change your shell's prompt and remove the name of the virtual environment that you were in.
===Sharing a virtual environment===
You can use '''pip freeze''' to list all the packages in a virtual environment and copy it to a '''requirement.txt.file'''
<pre>
pip freeze > requirements.txt
</pre>
Now you can create new virtualenv and after activating that virtual environment, install all the packages using the following command.
<pre>
pip install -r requirements.txt
</pre>

Latest revision as of 19:28, 18 December 2020

Python virtual environment is a method of creating an isolated environment for Python projects. It enables each project to have its own dependencies, regardless of what dependencies every other project has. To read more about Python virtual environments, click here.

Creating a Python Virtual Environment

Load one of the Python modules available on Cheaha in your environment.

[snoopy@c1 ~]$ module avail Python

-------------------------- /share/apps/rc/modules/all --------------------------
Python/2.7.10-goolf-1.7.20       Python/2.7.13-intel-2017a
Python/2.7.10-intel-2015b        Python/2.7.3-foss-2016a
Python/2.7.11-foss-2016a         Python/2.7.3-goolf-1.7.20
Python/2.7.11-foss-2016b         Python/2.7.5-goolf-1.7.20
Python/2.7.11-goolf-1.7.20       Python/2.7.8-intel-2015b
Python/2.7.11-intel-2015b        Python/2.7.9-goolf-1.7.20
Python/2.7.11-intel-2016a        Python/2.7.9-intel-2015b
Python/2.7.12-foss-2016a         Python/3.2.3-goolf-1.7.20
Python/2.7.12-foss-2016b         Python/3.5.1-foss-2016a
Python/2.7.12-intel-2015b        Python/3.5.1-intel-2016a
Python/2.7.12-intel-2016a        Python/3.6.1-intel-2017a
Python/2.7.13-GCCcore-6.3.0-bare Python/3.6.3-intel-2017a

Once you have loaded Python, we would use virtualenv to create and manage virtual environments.

[snoopy@c1 Python_Environments]$ module load Python/3.6.3-intel-2017a 
[snoopy@c1 Python_Environments]$ virtualenv test_environment
Using base prefix '/share/apps/rc/software/Python/3.6.3-intel-2017a'
New python executable in /data/user/snoopy/Python_Environments/test_environment/bin/python
Installing setuptools, pip, wheel...done.
[snoopy@c1 Python_Environments]$

Activating a Virtual Environment

Once a virtual environment has been created, you need to activate it to be in the virtual environment.

[snoopy@c1 Python_Environments]$ source test_environment/bin/activate
(test_environment) [snoopy@c1 Python_Environments]$

Activating the virtual environment will change your shell’s prompt to show what virtual environment you’re using, test_environment in the above case, and modify the environment so that you can install Python packages for that particular environment.

Maintaining a Virtual Environment

After this you can install the packages that you would like for this environment, using pip. pip is a package management system used to install and manage software packages written in Python.

(test_environment) [snoopy@c1 Python_Environments]$ pip install numpy
Collecting numpy
  Downloading numpy-1.14.0-cp36-cp36m-manylinux1_x86_64.whl (17.2MB)
    100% |████████████████████████████████| 17.2MB 77kB/s 
Installing collected packages: numpy
Successfully installed numpy-1.14.0
(test_environment) [snoopy@c1 Python_Environments]$ ls test_environment/lib/python3.6/site-packages/
easy_install.py         pip-9.0.1.dist-info  setuptools-38.4.0.dist-info
numpy                   pkg_resources        wheel
numpy-1.14.0.dist-info  __pycache__          wheel-0.30.0.dist-info
pip                     setuptools
(test_environment) [snoopy@c1 Python_Environments]$

You can use this method to install a Python application alongside all the dependencies that it requires.

Deactivating a Virtual Environment

After you are done using the virtual environment, you can use deactivate command to go back to your bash shell environemnt.

(test_environment) [snoopy@c1 Python_Environments]$ deactivate 
[snoopy@c1 Python_Environments]$

It would change your shell's prompt and remove the name of the virtual environment that you were in.

Sharing a virtual environment

You can use pip freeze to list all the packages in a virtual environment and copy it to a requirement.txt.file

pip freeze > requirements.txt

Now you can create new virtualenv and after activating that virtual environment, install all the packages using the following command.

pip install -r requirements.txt