[FIXED] Can't find "matplotlib.markers" even with Matplotlib installed

Issue

I realize this seems like a generic question, but all answers pointed to having two simultanious python installations - I already uninstalled the other one.

Currently I run my code from PyCharm 2017.1.5 (windows 10) with Python interpreter set as Python 3.6.1 (C:\Anaconda3\python.exe), i.e. I installed Anaconda3, which includes the matplotlib, and run from PyCharm using the Ananconda3-interpreter.

I've checked in Anaconda Navigator that matplotlib 2.0.2 is installed in the environment.

A minimal (non-working) example:

import matplotlib.pyplot as plt

plt.plot(range(10))
plt.show()

Returns the following error:

C:\Anaconda3\python.exe C:/Users/John/Documents/CPU/master/untitled/main11.py
Traceback (most recent call last):
  File "C:/Users/John/Documents/CPU/master/untitled/main11.py", line 1, in <module>
    import matplotlib.pyplot as plt
  File "C:\Anaconda3\lib\site-packages\matplotlib\pyplot.py", line 29, in <module>
    import matplotlib.colorbar
  File "C:\Anaconda3\lib\site-packages\matplotlib\colorbar.py", line 34, in <module>
    import matplotlib.collections as collections
  File "C:\Anaconda3\lib\site-packages\matplotlib\collections.py", line 37, in <module>
    import matplotlib.lines as mlines
  File "C:\Anaconda3\lib\site-packages\matplotlib\lines.py", line 28, in <module>
    from matplotlib.markers import MarkerStyle
ModuleNotFoundError: No module named 'matplotlib.markers'

Process finished with exit code 1

This ran fine 2 weeks ago, but not now. To my knowledge, I didn't change or update anything. The module loads correctly, but it seems to be a change in the module content? If so: How did that happen and how can I fix it?

Solution

@ImportanceOfBeingErnest lead me in the right direction. I post my solution here s.t. others may find the answer. The problem was a corrupted disk sector - an unlikely event of chance.

The problem was indeed in the matplotlib-package itself. Retrospectively, pointers to the issue were that errors in pre-distributed packages should not exist. If they do, external circumstances must have corrupted and the problem is not with the Python-installation itself.

I uninstalled matplotlib through Anaconda Prompt with conda remove matplotlib and re-installed with conda install matplotlib. This gave me this error:

(C:\Anaconda3) C:\Users\John>conda install matplotlib
[...]
ERROR conda.core.link:_execute_actions(337): An error occurred while installing package 'defaults::matplotlib-2.0.2-np112py36_0'.
OSError(22, 'Invalid argument') Attempting to roll back. 

OSError(22, 'Invalid argument')

Before @Ernest's comment, I thought it maybe had to do with non-ASCII in PATH or similar.

Instead I tried to reinstall Anaconda3 completely, restarted and found that part of the Anaconda3-folder weren't removed (the one containing the matplotlib).

Deleting it manually gave a Windows error 0x80070570. Following this post on ServerFault (the comment to OP) I ran a check and afterwards a repair from Windows Explorer GUI: Right-click on the drive in This PC --> Properties --> Tab Tools --> Check (repair appears if any errors are found).

After some restarts, reinstalling Anaconda3 from scratch and restarting again, I was able to run my project again!

Answered By - RasmusP_963