Error 1671 Python Node

[Operandus009]

Hi,

Labview 2018 user here. For some time, I was using Labview with Matlab script node to throw in some maths. I decided to switch to Python since the 2018 version of Labview supports it.

I tried some very basic tests ("Hello world" and some others) but when it comes to use one of my scripts (reading a three columns txt file), it sends me an error message :

Python Node in testlecturefichier.vi<APPEND>

Python returned the following error: <class 'SystemError'>
..\Objects\listobject.c:189: bad argument to internal function

The function is running flawlessly with the ipython console but not with the Labview node.

There are some additionnal infos :

- 3.6.2 python, 64 bits

- Labview 2018 64 bits

Maybe there is something obvious I missed. Can someone look through my code and maybe tell me what is wrong ?

Thank you in advance for your time.

[wiebe@CARYA]

Did you search the forum? This has been posted quite a few times before.

search the forum...

There are also (at least) 3 related knowledge base articles:

Error 1671 Occurred at Open Python Session

Error 1671 in LabVIEW When Calling Files Using Python Node

Error 1671 Using Python Script Stored on Network Drive in LabVIEW

[Operandus009]

Thank you for your answer.

Yes I searched for answers but none of the previous topics deal with my specific error. But I am wondering if you read my query before posting ...

[Operandus009 · Accepted solution]

Ok, found the error.

I was expecting an array but I was trying to return a list in the script so it wasn't working.

[Will_S.]

Just to add to this answer, since I just went through this: LabVIEW apparently can have trouble converting a list to an array unless it is explicitly built as a list.

For example, even though a slice returns a list, LabVIEW can give you Error 1671 if your python function returns it directly:

# Can cause Error 1671 in the LabVIEW Python node
def myfunc():
    return myData[:6]

Instead, do this: 

# Does not cause an error in the LabVIEW Python node
def myfunc():
    returnData = []
    for x in range(6):
        returnData.append(myData[x])

    return returnData

[derGogo]

Hum. I think I'm having exactly the same problem. Only I'd like to avoid modifying the python script, because 1- it's not mine, 2- it is used by other apps.

Can you think of a way to solve that on the Labview side?

my Python:

my labview code (right) and error (left), in which the keyword hinting to the same problem as yours is "Failed when trying to convert field into tuple at index 1":