Passing a variable from Excel to Python with XLwings

Question

I am trying write a simple user defined function in Python that I pass a value to from Excel via Xlwings. I ran across some examples with an Add-in that you need to import user defined functions, but that seems overly complex.

Why isn't my example working?

VBA:

Function Hello(name As String) As String
    RunPython ("import Test; Test.sayhi(name)")
End Function

Python (Test.py):

from xlwings import Workbook, Range

def sayhi(name):
    wb = Workbook.caller()
    return 'Hello {}'.format(name)

Error:

NameError: name 'name' is not defined

Answer 1

Make sure you're supplying the argument correctly:

RunPython ("import Test; Test.sayhi('" &  name & "')") 

Answer 2

The text inside RunPython() should be a valid python script. So the comment from "Tim Williams" is a quick solution. You just need to be careful to avoid ' character inside the name variable to break the python script.

If you need to write UDF (User Defined Function) a lot, or need to pass in value to get the output and then handle the result via VBA, try use ExcelPython instead of Xlwings.

Note, ExcelPython and Xlwings can work together, you can have both without conflict.

I think it's better you play the example to understand the difference. My understanding is limited to my knowledge, which might not be correct.

To summarize the difference:

• ExcelPython needs a installer to be installed, it is good in UDF, which helps if you want to pass arguments in and out, and the function is cached in memory, so later call will be very quick.
• Xlwings is simpler by just add the VBA module, no installer needed. It trigger Python in the background each time to run the script (each call starts a new process), in the script you can manipulate (read/write) Excel via COM.

I have the same question in the beginning, but later I find out using VBA in Excel side (intellisense) plus ExcelPython on UDF (simply process and return the data back) is a nice combination, so I think ExcelPython is only what I need.

As mentioned earlier, the 2 components have no conflict, you can have both. If the 2 author agree too, it is a good idea to combine them.