Installation

If your IT administrator or instructor has created an environment for your course, with allowed installed, then you may skip this section.

Preparation

  1. Open a Linux/macOS terminal or Windows PowerShell, in order to enter the commands given in these instructions.
  2. Enter python -V to check the version you have installed.
  3. If it’s 3.9 or earlier, download and install the latest version. However, to use pytype (see below) you must install Python 3.10 or 3.11.

Virtual environments

Like any other Python package, allowed can be installed in your default global environment, but should preferably be installed in a new or existing virtual environment, e.g. the one for the course you are studying or teaching. A virtual environment is a folder with the software you need for one or more projects. This helps ensuring that you always use the right versions of the right packages for each project.

  1. To create a virtual environment, enter python -m venv path/to/folder.

The folder you indicate will be created if it doesn’t exist. For example, if you want to keep all virtual environments in subfolders of ~/environments, you would create a new virtual environment for course CS101 with python -m venv ~/environments/cs101.

Virtual environments need to be activated in order install software in them.

  1. To activate a virtual environment enter
    • source path/to/folder/bin/activate in Linux/macOS
    • path/to/folder/scripts/Activate in Windows.

For our example, it would be source ~/environments/cs101/bin/activate or ~/environments/cs101/scripts/Activate. After activating, the command prompt becomes (folder), e.g. (cs101), to show which environment is active.

You must activate a virtual environment every time you want to install further software into it or use the software that is installed in it.

  1. Once you’re done using a virtual environment, close the terminal/PowerShell or type deactivate.

For more details on why one should use virtual environments and how to use them, we recommend reading the first two sections of Real Python’s tutorial.

Installing

The following instructions will install allowed and optional additional software in your current environment, whether it’s the global environment or an active virtual environment.

  1. Enter pip install allowed.

allowed can check Python code in .py files and in .ipynb files (Jupyter notebooks). If you want to check Jupyter notebooks that have IPython commands like %timeit and %run, then you need IPython.

  1. Enter pip show ipython to check if your current environment has IPython installed.
  2. If you get a message that there’s no such package, then enter pip install ipython.

To check method calls of the form variable.method(...), allowed needs the pytype package, to know the type of variable. pytype is only available for Linux and macOS.

  1. Enter pip show pytype to see if pytype is already installed.
  2. If it isn’t, enter pip install pytype.
⇧ Start Usage ⇨