Python Node in LV2018

[Steve_555]

I am trying to use the new native support for Python in LV2018.  I have Python 3.6 installed and have added the corresponding DLL to the path as indicated in the LV documentation.  I am able to open a Python session using the "Open Python Session Function" node and close that same session using the "Close Python Session Function" node, all without errors, which feels like a big enough accomplishment at the moment.

When I try and actually use the session with a Python Node to run a function that is built-in to Python (print) I get an error:

Error 1667 occurred at Python Node in pythonTest.vi

Possible reason(s):

LabVIEW: (Hex 0x683) The specified Python module could not be imported.

Module Path: C:\Python36\python36.dll
Function Name: print
Python returned the following error: <class 'ModuleNotFoundError'>
No module named 'python36'

In the example above I set the module to the Python DLL.  In the end, I'm not really sure what to set the module so that I can print "hello world!"

I'm effectively trying to run:

print("Hello World!") 

Just to so that I know I have a decent starting point.

Does anyone have any advice?

Thanks,

Steve

[Gregory]

---

@Steve_555 wrote:

Module Path: C:\Python36\python36.dll
Function Name: print
Python returned the following error: <class 'ModuleNotFoundError'>
No module named 'python36'

---

Do you have a file at that path?

[chericks]

Hi Steve,

I defined a simple function that returned the string "hello world!", saved the function in a .py file, and provided the file path to the Python Node.  

Hope this helps!

Chad

Screenshot

[Steve_555]

Hi Chad,

I realize my mistake now.  I was thinking that I could pass individual lines of Python script to the Python node and it would run them.  I see now that it can only execute functions from within a module.  

Thank you for the detailed answer,

Steve

[luboss333]

Hello

Did you try to run external libraries like numpy, scipy or matplotlib. I have libraries installed in the sys path and I tried to import them into a file that is defined in the path of Python node. Labview responded with the 'ModuleNotFoundError' error No module named 'numpy'.  Can I ask for a simple example VI of how to use external Python libraries.

Thank you

[chericks]

Hi luboss333,

I was able to use numpy, scipy, and matplotlib. I've attached a simple example. Does it work for you?

Hope this helps!
Chad

[chericks]

I probably should have explained the two additional LabVIEW VIs.  As described in this forum thread, one way to embed a matplotlib graph within LabVIEW is the following:

1) In Python: write the plot to a file using matplotlib's savefig()

2) In LabVIEW: display the plot using Read JPEG File.vi (or Bitmap/PNG) and Draw Flattened Pixmap.vi

Best regards!

Chad

[luboss333]

Thank you very much for the answer

I understand the idea  of VI and Py file. I've also tried this, and it's interesting that Labview still writes the same error -> import numpy as np, "ModuleNotFoundError: No module named 'numpy'. It looks like Labview can not find the numpy in system path. I have installed Anaconda (ver 3.6, 32 bit) in the system path. I do not know if there is any setting in Labview to change of interpreter of Python.

[chericks]

Hi luboss333,

I think you're close to solving the problem.  On my computer the package for numpy is installed in the following Anaconda3 directory: 

C:\Users\chericks\Anaconda3\pkgs\numpy-1.14.0-py36h4a99626_1\Lib\site-packages\numpy

LabVIEW should be able to find the module by searching the system path.  Looking at my Environment Variables, I placed the Anaconda3 directory in both User variables and System variables.

Variable: Path
Value: C:\Users\chericks\Anaconda3;

Do you have the Anaconda directory shown there?

Attached below are stackoverflow forum posts related to calling Python and getting an import error:

https://stackoverflow.com/questions/15514593/importerror-no-module-named-when-trying-to-run-python-s...
https://stackoverflow.com/questions/3701646/how-to-add-to-the-pythonpath-in-windows

Hope this helps!

Chad

[luboss333]

Thank you 

I changed the path in the windows variable and now it works. I have next problem with matlplot lib :). 

You used the command matplotlib.use('Agg') in py file generating image without having a window appear.

When running a program without this command, Labview generates a QT plugin error in windows.

I need to open graphs in external window like in the python interpreter. 

Do you have any idea how to solve it ? 

Thank you