Matplotlib Import fails after successive run of custom tool

Question

Hey all - I have a custom toolbox that imports Matplotlib and numpy to do some charting.  The tool will run perfect upon opening and on an initial run.  Each successive run in an open ArcMap session gives me the error: import matplotlib as plt KeyError: u'PolyCollection'

Any ideas or help is appreciated!

SilasFrantz · Answer

I came across this problem writing a custom tool for ArcGIS 10.6 and distilled it to the two lines below.

import matplotlib.pyplot as plt

plt.figure()

When run from ArcMap, this would succeed the first time then error on subsequent attempts to import the module...

File "C:\Python27\ArcGIS10.6\lib\site-packages\matplotlib\quiver.py", line 171, in <module>

""" % docstring.interpd.params

KeyError: u'PolyCollection'

Ended up solving by repairing matplotlib using the ArcGIS Setup wizard. Not sure what may have been the cause.

DanPatterson_Retired · Answer

You might want to have a look at the variables you are using in your script... one may be overwriting a previously established namespace.  Modules are only reloaded if needed and if the namespace isn't claimed.

I don't know what version of python you are using but check for 'reload' in python 2 and the importlib reload module in python 3.  If the namespace isn't the problem, then reload the modules at the end of the script.

Also, import numpy before matplotlib because matplotlib doesn't import the whole numpy module and you want numpy's namespace to be claimed before anything else tries to claim it

JoshStreufert · Answer

Here are my import statements... Like I said, runs fine the first time but subsequent times python throws an error like it cant load the library. import arcpy import os import datetime import exceptions, sys, traceback import matplotlib.pyplot as plt import numpy as np import math‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍