Pip Version#

If an error message appears after trying to run pip install autolens first make sure you are using the latest version of pip.

pip install --upgrade pip
pip3 install --upgrade pip

NumPy / numba#

The libraries numpy and numba can be installed with incompatible versions.

An error message like the one below occurs when importing PyAutoGalaxy:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/jammy/venvs/PyAutoMay2/lib/python3.8/site-packages/autolens/", line 1, in <module>
    from autoarray import preprocess
  File "/home/jammy/venvs/PyAutoMay2/lib/python3.8/site-packages/autoarray/", line 2, in <module>
    from . import type
  File "/home/jammy/venvs/PyAutoMay2/lib/python3.8/site-packages/autoarray/", line 7, in <module>
    from autoarray.mask.mask_1d import Mask1D
  File "/home/jammy/venvs/PyAutoMay2/lib/python3.8/site-packages/autoarray/mask/", line 8, in <module>
    from autoarray.structures.arrays import array_1d_util
  File "/home/jammy/venvs/PyAutoMay2/lib/python3.8/site-packages/autoarray/structures/arrays/", line 5, in <module>
    from autoarray import numba_util
  File "/home/jammy/venvs/PyAutoMay2/lib/python3.8/site-packages/autoarray/", line 2, in <module>
    import numba
  File "/home/jammy/venvs/PyAutoMay2/lib/python3.8/site-packages/numba/", line 200, in <module>
  File "/home/jammy/venvs/PyAutoMay2/lib/python3.8/site-packages/numba/", line 140, in _ensure_critical_deps
    raise ImportError("Numba needs NumPy 1.21 or less")
ImportError: Numba needs NumPy 1.21 or less

This can be fixed by reinstalling numpy with the version requested by the error message, in the example numpy 1.21 (you should replace the ==1.21.0 with a different version if requested).

pip install numpy==1.21.0

Pip / Conda#

If you are trying to install via pip but still haing issues, we recommend you try to install via conda instead, or visa versa.


If you are still having issues with installation, please raise an issue on the autolens_workspace issues page with a description of the problem and your system setup (operating system, Python version, etc.).

Current Working Directory#

PyAutoLens scripts assume that the autolens_workspace directory is the Python working directory. This means that, when you run an example script, you should run it from the autolens_workspace as follows:

cd path/to/autolens_workspace (if you are not already in the autolens_workspace).
python3 examples/model/beginner/

The reasons for this are so that PyAutoLens can:

  • Load configuration settings from config files in the autolens_workspace/config folder.

  • Load example data from the autolens_workspace/dataset folder.

  • Output the results of models fits to your hard-disk to the autolens/output folder.

If you have any errors relating to importing modules, loading data or outputting results it is likely because you are not running the script with the autolens_workspace as the working directory!

Matplotlib Backend#

Matplotlib uses the default backend on your computer, as set in the config file:


If unchanged, the backend is set to ‘default’, meaning it will use the backend automatically set up for Python on your system.

backend = default

There have been reports that using the default backend causes crashes when running the test script below (either the code crashes without a error or your computer restarts). If this happens, change the config’s backend until the test works (TKAgg has worked on Linux machines, Qt5Agg has worked on new MACs). For example:

backend = TKAgg