Working with Python we have a lot of libraries or dependencies.
Our projects use just a version of each dependency. It’s very important to decouple the list of dependencies between projects. Otherwise, our applications could have an undesired behaviour.
Los entornos virtuales de Python nos ayudan en dicha tarea.
Prerequisites:
- Python
- Pip
Virtual environment
We will use the command virtualenv to work with virtual environments in Python.
If you have not installed “virtualenv”, install it:
❯ pip install virtualenv
Creation of an environment called venv
❯ python -m venv venv
To use the environment:
❯ source venv/bin/activate
Now, we will list the dependencies in our environment, we should have only the basics of a new installation:
❯ pip list
Package Version
---------- -------
pip 21.2.3
setuptools 57.4.0
Dependencies file
The file requeriments.txt has the list of dependencies necessary to run our application.
How to create the file
The easiest way is to start a new environment and install all the needed dependencies. In this demo, I will install pandas.
❯ pip install pandas
If we list now the libraries, we can see all of them:
❯ pip list
Package Version
--------------- -------
numpy 1.23.0
pandas 1.4.3
pip 21.2.3
python-dateutil 2.8.2
pytz 2022.1
setuptools 57.4.0
six 1.16.0
When we have the complete list installed, we will use the freeze command to generate the file:
❯ pip freeze > requirements.txt
❯ cat requirements.txt
numpy==1.23.0
pandas==1.4.3
python-dateutil==2.8.2
pytz==2022.1
six==1.16.0
How to install the dependencies
Using the command pip install, we can install all the dependencies indicated in our file:
❯ pip install -r requirements.txt
Close the virtual env
To close the virtual environment in Python we only have to use the command deactivate.
❯ deactivate