When developing software, you often need a specific combination of Python libraries. Sometimes this is difficult, because you require a specific version of a library, want to test your program on multiple Python versions, or simply need to develop your program further, while a stable version is installed on the same machine. In these cases, virtual environments come to the rescue.
A virtual environment manages multiple parallel installations of Python interpreters and libraries, so that you can switch between them. The virtual environment consists of a folder per project, in which Python libraries for that project are installed.
There are many Python tools to manage virtual environments: venv, virtualenv, Pipenv and Poetry. A beginner-friendly tool is to use conda. If you haven't installed Anaconda already, you can find the Miniconda installer at https://conda.io/miniconda.html.
Once the installer finishes and you open a new terminal, you should see (base) before the prompt:
:::bash
(base) ada@adas_laptop:~$
This means you are in an virtual environment called "base".
Let's create a new one for a project that requires the tqdm package:
:::bash
conda create -n tqdm
Behind the scenes conda creates a new subdirectory. This is where libraries for your project will be stored. There are also scripts to activate the environment.
To start working with your project, type:
:::bash
conda activate myproject
You should see a (myproject) appearing at your prompt. Now, whenever you use pip to install something, it will be installed only for myproject.
Now check which libraries you have installed:
:::bash
pip freeze
You can install additional libraries with pip or conda:
:::bash
conda install pandas
When you want to switch back to the base environment, type:
:::bash
conda activate base
The virtual environment is specific for a terminal session. Thus, you can work on as many projects simultaneously as you have terminals open.