How to Install and Use virtualenv with Python 3

Virtualenv is a tool used to create an isolated Python environment. This environment has its own installation directories and environment. This doesn’t share libraries with other environments. It is very helpful for the application required separate environments on the same server. The Virtualenv is the easiest and recommended way to configure a custom Python environment. This tutorial will help you to how to create a virtual environment for your Python application and use this.

Prerequisites

You must have the following packages installed on your system.

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• Python 3
• PIP

Install Virtualenv with Python 3

You must have Python 3 and PIP installed on your system. We use virtualenv package to create virtual environment for the Python applications. So first install virtualenv Python module using command:

pip3 install virtualenv

Collecting virtualenv
  Downloading https://files.pythonhosted.org/packages/f7/69/9a07/virtualenv-16.7.4-py2.py3-none-any.whl (3.3MB)
    100% |████████████████████████████████| 3.3MB 448kB/s
Installing collected packages: virtualenv
Successfully installed virtualenv-16.7.4

Create Virtual Environment

Search for the Python3 binary location on your system. Use the following command to find the Python 3 binary file location on your system.

which python3

/usr/bin/python3

As per the above command, Python 3 binary is available at /usr/bin/python3.

Next, switch to your Python application directory

cd /var/webapps/

Then, create a separate environment for your Application. You can change the environment directory name (isoEnv used in below example) as per your choice. You can also define the environment directory on a different location.

virtualenv -p /usr/bin/python3 isoEnv


Running virtualenv with interpreter /usr/bin/python3
Already using interpreter /usr/bin/python3
Using base prefix '/usr'
New python executable in /var/webapps/isoEnv/bin/python3
Also creating executable in /var/webapps/isoEnv/bin/python
Installing setuptools, pip, wheel...
done.

The above command will creates a separate environment for the Python binary file. You can access it by typing python only.

Activate Virtual Environment

You need to activate virtual environment before using it. This will insure to install all modules and configurations to virtual environment only. To activate the virtual environment, execute:

source isoEnv/bin/activate

The name of the current virtual environment appears to the left of the prompt. Your prompt will be look like (isoEnv) root@tecadmin$

To verify the correct Python version, run the following:

(isoEnv) root@tecadmin$ python -V

Python 3.6.8

Any package that you install using pip is now placed in the virtual environments project folder, isolated from the global Python installation.

Use pip3 to install a module:

(isoEnv) root@tecadmin$ pip3 install <module>

You can use ‘nose’ if you’re going to work with openstack. For example:

(isoEnv) root@tecadmin$ pip3 install nose

Collecting nose
  Downloading https://files.pythonhosted.org/packages/15/d8/dd071918c040f50fa1cf80da16423af51ff8ce4a0f2399b7bf8de45ac3d9/nose-1.3.7-py3-none-any.whl (154kB)
     |████████████████████████████████| 163kB 18.6MB/s
Installing collected packages: nose
Successfully installed nose-1.3.7

Deactivate virtualenv Environment

After finishing your work inside the virtual environment, simply exit from this by typing deactivate command. You will get the users to default shell.

(isoEnv) root@tecadmin$ deactivate

Delete virtualenv Environment

If your application no more required the virtual environment, You can delete this. To delete the environment simply delete the environment directory.

rm -rf isoEnv

Conclusion

In this tutorial, you have learned about configuration of the Python virtual environment on Linux system.