$ pip install virtualenv # install the virtual env
$ virtualenv myvirtualenvname # create the virtual env
$ source myvirtualenvname/bin/activate # activate the environment

Once your virtualenv is activated by the source myvirtualenvname/bin/activate you can install the package by the following command.

Dev option will also install pytest so you can add and run your tests.

if you are using zsh shell you have to use escacpe characters for brackets.

$ pip install -e .\[dev\]

otherwise you can install it as follows

$ pip install -e .[dev]

While you are an the root directory just run the following command. This will exclude pytest package from the installation.

$ pip install -e .