Working in a Python virtualenv

In this article we will discuss working in a virtual environment.

We covered installing virtualenv in the previous article

We are in the directory virtualenvs inside which we created a virtual environment for Python3 called test_env

To activate the virtual environment test_env from the standard cmd in Windows execute

test_env\Scripts\activate.bat

If you are in PowerShell, execute

test_env\Scripts\activate.ps1

And if you are on Linux execute

. test_env/bin/activate

On successful activation the name of the virtual environment appears in parentheses on the left of the command prompt (test_env)

(test_env) PS C:\Users\Andrei\virtualenvs>

If nothing happened, read the advice in my article

«Difficulties when working with Python»

The first thing to do after entering a new environment is to check the Python and Pip versions

python -V

Python 3.8.2

pip -V

pip 20.1.1 from C:\Users\Andrei\virtualenvs\test_env\lib\site-packages\pip (python 3.8)

Let's check which modules are installed in the new virtual environment

python -m pip list

Package Version ---------- ------- pip 20.1.1 setuptools 46.4.0 wheel 0.34.2

There are only three modules, which means that something has indeed changed.

Compare this with the number of modules installed in the system from the lesson pip

Let's install requests in the virtual environment

python -m pip install requests

Collecting requests Downloading requests-2.23.0-py2.py3-none-any.whl (58 kB) |████████████████████████████████| 58 kB 609 kB/s Collecting urllib3!=1.25.0,!=1.25.1,<1.26,>=1.21.1 Downloading urllib3-1.25.9-py2.py3-none-any.whl (126 kB) |████████████████████████████████| 126 kB 2.2 MB/s Collecting chardet<4,>=3.0.2 Downloading chardet-3.0.4-py2.py3-none-any.whl (133 kB) |████████████████████████████████| 133 kB 2.2 MB/s Collecting certifi>=2017.4.17 Downloading certifi-2020.4.5.2-py2.py3-none-any.whl (157 kB) |████████████████████████████████| 157 kB 3.2 MB/s Collecting idna<3,>=2.5 Downloading idna-2.9-py2.py3-none-any.whl (58 kB) |████████████████████████████████| 58 kB 1.6 MB/s Installing collected packages: urllib3, chardet, certifi, idna, requests Successfully installed certifi-2020.4.5.2 chardet-3.0.4 idna-2.9 requests-2.23.0 urllib3-1.25.9

Let's check which packages were installed

python -m pip list

Package Version ---------- ---------- certifi 2020.4.5.2 chardet 3.0.4 idna 2.9 pip 20.1.1 requests 2.23.0 setuptools 46.4.0 urllib3 1.25.9 wheel 0.34.2

requests pulled in four more packages: certifi, chardet, idna, urllib3

You can check where requests was installed in this environment with the command

python -m pip show requests

Name: requests Version: 2.23.0 Summary: Python HTTP for Humans. Home-page: https://requests.readthedocs.io Author: Kenneth Reitz Author-email: me@kennethreitz.org License: Apache 2.0 Location: c:\users\andrei\virtualenvs\test_env\lib\site-packages Requires: chardet, certifi, urllib3, idna Required-by:

To leave the virtual environment, use the command

deactivate

python -m pip show requests

span class="yellow">WARNING: Package(s) not found: requests

You can see that requests is not installed globally at all

Starting with Python 3.6, it is recommended to create virtual environments with the command

python -m venv myvenv

The environment is activated in the same way

myvenv\Scripts\Activate.ps1

(myvenv) PS C:\Users\Andrei\virtualenvs>

I don't know about you, but in my PowerShell (myvenv), created with venv, is highlighted in green, while test_env, created with virtualenv, stays grey.

Deleting the virtual environment

To delete the virtual environment, just delete the folder

Article author: Andrei Olegovich