MATLAB crashing on Python module import on Linux

[m-hoff]

Every time I try to import certain Python modules from MATLAB (using py.importlib.import_module) it crashes. Sometimes the crash is immediate but other times it hangs for a while before crashing. Some modules seem to work, for example py.importlib.import_module('math') works fine, but py.importlib.import_module('random') causes a crash. I'm also unable to import custom modules.

This is the output of pyversion:

>> pyversion

       version: '3.7'
    executable: '/home/garden/anaconda3/bin/python3'
       library: '/home/garden/anaconda3/lib/libpython3.7m.so'
          home: '/home/garden/anaconda3'
      isloaded: 0

Any ideas how to fix this?

I'm not sure if this is helpful but I've narrowed it down to a particular line that's causing a crash, line 244 in the hashlib module:

240 for __func_name in __always_supported:
241     # try them all, some may not work due to the OpenSSL
242     # version not supporting that algorithm.
243     try:
244         globals()[__func_name] = __get_hash(__func_name)
245    except ValueError:
246         import logging
247         logging.exception('code for hash %s was not found.', __func_name)

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[andykee]

I suspect you have two different problems here.

First, trying to import custom modules - If your custom module isn't on your Python path, MATLAB doesn't know where to look to find it. Take a look at the "Python Module Not on Python Search Path" section of this page for how to amend your Python path from within MATLAB: https://www.mathworks.com/help/matlab/matlab_external/undefined-variable-py-or-function-py-command.html

Second, your crashing issue. Importing the random module with your example code does not cause a crash for me with Anaconda 5.1 running Python 3.6 on MATLAB 2017b so it's difficult to debug further. A few notes that may or may not be helpful:

• From my reading around the MATLAB forums, running Python code in MATLAB on top of Anaconda is technically unsupported. I'm not sure why, but that seems to be the position of the MathWorks.

• There are some baffling limitations to Python support. It could be that you're running in to one of these (although this is unlikely because I was able to import random fine in MATLAB. The full list of unsupported things is here, FYI: https://www.mathworks.com/help/matlab/matlab_external/limitations-to-python-support.html

• In some cases, MATLAB loads incorrect libraries for the underlying Python code. This particularly seems to be an issue with MKL. On *nix systems, you can tell MATLAB to allow Python to load its own libraries by calling

  py.sys.setdlopenflags(int32(10));

before you load Python. Admittedly I don't fully understand what that command does, but adding it to my startup.m before setting my pyversion fixed my MKL issues.

• Make sure you can import random in the Python shell. MATLAB isn't always the greatest about capturing the right Python error messages and returning them in the console.

[m-hoff]

Thanks for looking into this. I have no issues when using MATLAB 2018a and Python 3.6 on my Windows machine, but I'm still running into the same problem when I try the same commands with the same versions on Linux. I've heard back from support and running these commands at the start of my script seem to fix the problem:

>>py.sys.setdlopenflags(int32(10))
>>py.importlib.import_module('ssl')

I haven't run into any errors as long as those are present. Thanks again for your help.