pip and virtualenv

The recommended practice for installing dependencies is to create a virtualenv. A virtualenv (https://packaging.python.org/guides/installing-using-pip-and-virtualenv/) acts like a complete separate Python installation from the one that comes with your operating system, making it safe to install the packages required by your application without risk of breaking your system Python or tools.

Now we will learn how to create a virtual environment and install pytest using pip. If you are already familiar with virtualenv and pip, you can skip this section:

1. Type this in your Command Prompt to create a virtualenv:

λ python -m venv .env

2. This command will create a .env folder in the current directory, containing a full-blown Python installation. Before proceeding, you should activate the virtualenv:

λ source .env/bin/activate

Or on Windows:

λ .env\Scripts\activate

This will put the virtualenv Python in front of the $PATH environment variable, so Python, pip, and other tools will be executed from the virtualenv, not from your system.

3. Finally, to install pytest, type:

λ pip install pytest

You can verify that everything went well by typing:

λ pytest --version
This is pytest version 3.5.1, imported from x:\fibo\.env36\lib\site-packages\pytest.py

Now, we are all set up and can begin!