Hello,
i wanted to create an image output in a python scripting node [Python 3 - Anaconda] for fast prototyping. This has always worked so far, but after an update to KNIME 3.6.0 this now fails.
Code:
import matplotlib.pyplot as plt
plt.figure()
plt.plot([1,2,3,4])
plt.ylabel(‘some numbers’)
plt.show()
Error:
Traceback (most recent call last):
File “C:\Program Files\KNIME\plugins\org.knime.python2_3.6.0.v201807061638\py\PythonKernelBase.py”, line 278, in execute
exec(source_code, self._exec_env, self._exec_env)
File “”, line 7, in
File “C:\ProgramData\Anaconda3\lib\site-packages\matplotlib\pyplot.py”, line 253, in show
return _show(*args, **kw)
File “C:\ProgramData\Anaconda3\lib\site-packages\matplotlib\backend_bases.py”, line 208, in show
cls.mainloop()
File “C:\ProgramData\Anaconda3\lib\site-packages\matplotlib\backends\backend_qt5.py”, line 1118, in mainloop
signal.signal(signal.SIGINT, signal.SIG_DFL)
File “C:\ProgramData\Anaconda3\lib\signal.py”, line 47, in signal
handler = _signal.signal(_enum_to_int(signalnum), _enum_to_int(handler))
ValueError: signal only works in main thread
We introduced threading for Python 3 in KNIME Python 3.6.0 to support some use cases that came with KNIME Deep Learning - Keras, which is built on top of your Python integration.
You could try to change to Python 2 via the node’s Options tab, if Python 2 is okay with you.
For Python 3, there is no workaround as far as I know, unfortunately.
Thanks for reporting that issue! And sorry for all the trouble. We’ll try to move script execution back to the main thread.
Hi Marcel,
I switched the whole system and lecture to Python3 (and only Python 3). This is a nightmare and a lot of extra work. .Could you please give me an indication when its will be fixed an released?
We’ll target the next bug fix release, i.e., 3.6.2. I can’t give you a timeline, unfortunately, as we just released 3.6.1.
If the plot does not need to be interactive, you could also use the Python View node to output the plot as an image.
Otherwise, downgrading to KNIME 3.5.3 seems to be the only solution at the moment, I’m afraid. Please find a download link here.
I’ll keep you posted on our progress. Nightly builds that contain a respective fix will be available earlier, if those are an option for you.
