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Python Data Science Basics Charts and Tables Bar Charts

Posted by Iain Simmons
Iain Simmons
Treehouse Moderator 32,305 Points

'alloc: invalid block:' error when generating bar chart with matplotlib

After downloading the files from Workspaces and running s5v2.py on my local Windows 7 machine, I got the following crazy, non-descriptive error:

alloc: invalid block: 040F4158: 80 4

After quite a bit of research I found that I could get it to work if I changed the 'backend' that matplotlib was using from TkAgg to Qt4Agg.

To do that I created a matplotlibrc file in the .matplotlib directory in my home/user directory, and added/changed the following line:

backend      : Qt4Agg

Here is some matplotlib documentation that explains what is going on:

Hope that helps anyone else having a similar problem!

1 Answer

Dennis Mayo
Dennis Mayo
13,508 Points

I had a very similar problem with my build on Windows 10. I should add that I was working through this lesson locally and not in workspaces.

I followed the instructions in this post but ultimately ended up with an error "ImportError: No module named 'PySide'.

I corrected that error by doing pip install pyside from the command prompt. The build works perfectly and the graphs look fantastic. Thinking a little more about the initial error it may have been a bad install on my end on whatever module the original code was using.

Iain Simmons
Iain Simmons
Treehouse Moderator 32,305 Points

I was also using Windows. I think the setup will just be a bit different for each operating system, which isn't ideal when coding, but sometimes unavoidable.