This is an issue with the latest version of matplotlib (3.3) -- you should downgrade your matplotlib to 3.2 or you can try installing the latest yt from source, which has a fix for this problem.

On Mon, Nov 2, 2020 at 10:24 AM Siegfried Vanaverbeke <> wrote:

I am testing a script on both windows and linux, but the latest version of yt seems to have a conflict with matplotlib:

/home/siegfried/anaconda3/envs/science/lib/python3.8/ MatplotlibDeprecationWarning: The global colormaps dictionary is no longer considered public API.
Traceback (most recent call last):
  File "", line 3, in <module>
    import yt
  File "/home/siegfried/anaconda3/envs/science/lib/python3.8/site-packages/yt/", line 63, in <module>
    from yt.fields.api import \
  File "/home/siegfried/anaconda3/envs/science/lib/python3.8/site-packages/yt/fields/", line 19, in <module>
    from . import angular_momentum
  File "/home/siegfried/anaconda3/envs/science/lib/python3.8/site-packages/yt/fields/", line 26, in <module>
    from .vector_operations import \
  File "/home/siegfried/anaconda3/envs/science/lib/python3.8/site-packages/yt/fields/", line 32, in <module>
    from yt.geometry.geometry_handler import \
  File "/home/siegfried/anaconda3/envs/science/lib/python3.8/site-packages/yt/geometry/", line 29, in <module>
    from yt.utilities.parallel_tools.parallel_analysis_interface import \
  File "/home/siegfried/anaconda3/envs/science/lib/python3.8/site-packages/yt/utilities/parallel_tools/", line 30, in <module>
    from yt.data_objects.image_array import ImageArray
  File "/home/siegfried/anaconda3/envs/science/lib/python3.8/site-packages/yt/data_objects/", line 18, in <module>
    from yt.visualization.image_writer import write_bitmap, write_image
  File "/home/siegfried/anaconda3/envs/science/lib/python3.8/site-packages/yt/visualization/", line 29, in <module>
    import yt.utilities.png_writer as pw
  File "/home/siegfried/anaconda3/envs/science/lib/python3.8/site-packages/yt/utilities/", line 13, in <module>
    import matplotlib._png as _png
ModuleNotFoundError: No module named 'matplotlib._png'

It tries to import a package that doesn't exist.  Any idea how this mistake came about ?

warmest regards,

Siegfried Vanaverbeke
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