Virtual Environments

Creating a Python environment using Anaconda

Since different Python packages have different dependencies, installing multiple packages on the same machine can cause issues. For example, mrsimulator requires at least numpy v1.17 but some-other-library might require exactly numpy v1.15. These two libraries would likely throw errors when run in the same environment.

For this reason, we recommend using an environment manager, like venv or anaconda. We will look at anaconda for its simple commands. Installation instructions can be found on the anaconda documentation page.


Anaconda is a robust package and environment management program, but it does require a significant amount of space on disk (>400mb). If you need a lightweight environment manager and are confident with Python, we recommend looking at Python’s venv documentation.

Once Anaconda is installed, create a new environment by running

$ conda create -n <name> python=3.9

where <name> is the desired name of your environment. Each environment can have a Python version specified after python=. We recommend using python=3.9. Next activate the environment by running

$ conda activate <name>

The current environment name is reflected in the leftmost portion of a line. On MacOS, an environment named mrsimulator-0.7 should look like

(mrsimulator-0.7) nmruser@machine $

If you are using a code editor or IDE, the current environment should be displayed somewhere on the window. For VS Code, the environment name and Python version are shown in the bottom-left corner.

To install mrsimulator in this new environment, follow the installation instructions. Mrsimulator and any other libraries will only be installed in the active environment. This way different projects can run in separate environments.

To exit the environment run

$ conda deactivate

To start using mrsimulator again, simply activate the environment in which it was installed.

Packages installed in an environment remain installed between sessions and won’t interfere with packages in other environments.