Is there a way to call a Python code in Excel-VBA?

Question

I have an Excel file (Main.xlsm) containing macros. I have a Python file (python.py) to generate a subsidiary Excel file (sub.xlsx) which I would further call in the macros of Main.xlsm-file. This sub.xlsx-file which is generated by the run of python.py is saved in the same working directory.

Now I want to make this python.py to be executed during the run of the Main.xlsm macros and then use this xlsx-file. I basically want to reduce the step of executing python.py externally. Is there a command for that? I am new to VBA.

Answer 1

The simplest way is to run the python interpreter with the Shell command

Shell ("python.exe " & yourScript & " " & arguments)

Answer 2

Yes, there is. My preferred way of doing this is through xlwings (https://www.xlwings.org/), but there are several other options as well. XlWings is great because it's free, open source and easy to use, with great documentation. There are some feature limitations though, so you'd have to check if it fits your needs.

Answer 3

There are multiple ways tu run a python script with VBA depending on whether you need to wait for the end of the execution and know if it went without error.

With Shell, asynchronous with console:

Public Sub RunPython(file As String, ParamArray args())
  Shell "python.exe """ & file & """ " & Join(args, " ")
End Sub

With Shell, synchronous without console:

Public Function RunPython(file As String, ParamArray args())
  Shell "pythonw.exe """ & file & """ " & Join(args, " ")
End Function

With WScript.Shell, synchronous without console and with exit code:

Public Function RunPython(file As String, ParamArray args()) As Long
  Dim obj As Object
  Set obj = CreateObject("WScript.Shell")
  RunPython = obj.Run("pythonw.exe """ & file & """ " & Join(args, " "), 0, True)
End Function

Answer 4

I had a whole Python month on my blog right here. I establish a pattern which I call the gateway class which is a COM enabled Python class, it will register itself if run from the command line and once registered is instantiated with CreateObject("foo.bar").

Here is a good example of VBA calling a Python class that uses some scipy functions

import numpy as np
import pandas as pd
from scipy.stats import skewnorm


class PythonSkewedNormal(object):
    _reg_clsid_ = "{1583241D-27EA-4A01-ACFB-4905810F6B98}"
    _reg_progid_ = 'SciPyInVBA.PythonSkewedNormal'
    _public_methods_ = ['GeneratePopulation', 'BinnedSkewedNormal']

    def GeneratePopulation(self, a, sz):
        # https://docs.scipy.org/doc/numpy-1.15.1/reference/generated/numpy.random.seed.html
        np.random.seed(10)
        # https://docs.scipy.org/doc/scipy-0.19.1/reference/generated/scipy.stats.skewnorm.html
        return skewnorm.rvs(a, size=sz).tolist()

    def BinnedSkewedNormal(self, a, sz, bins):
        # https://docs.scipy.org/doc/numpy-1.15.1/reference/generated/numpy.random.seed.html
        np.random.seed(10)
        # https://docs.scipy.org/doc/scipy-0.19.1/reference/generated/scipy.stats.skewnorm.html
        pop = skewnorm.rvs(a, size=sz)
        bins2 = np.array(bins)
        bins3 = pd.cut(pop, bins2)

        table = pd.value_counts(bins3, sort=False)

        table.index = table.index.astype(str)

        return table.reset_index().values.tolist()

if __name__ == '__main__':
    print("Registering COM server...")
    import win32com.server.register
    win32com.server.register.UseCommandLine(PythonSkewedNormal)

and the calling VBA code

Option Explicit

Sub TestPythonSkewedNormal()

    Dim skewedNormal As Object
    Set skewedNormal = CreateObject("SciPyInVBA.PythonSkewedNormal")

    Dim lSize As Long
    lSize = 100

    Dim shtData As Excel.Worksheet
    Set shtData = ThisWorkbook.Worksheets.Item("Sheet3") '<--- change sheet to your circumstances
    shtData.Cells.Clear

    Dim vBins
    vBins = Array(-5, -4, -3, -2, -1, 0, 1, 2, 3, 4, 5)

    'Stop
    Dim vBinnedData
    vBinnedData = skewedNormal.BinnedSkewedNormal(-5, lSize, vBins)

    Dim rngData As Excel.Range
    Set rngData = shtData.Cells(2, 1).Resize(UBound(vBins) - LBound(vBins), 2)

    rngData.Value2 = vBinnedData

    'Stop

End Sub

Full commentary can be found at the original blog entry here

The advantage here is that there is no shelling. When the code it returns, you know it has finished, with shelling once has to check if the shelled process has ended etc. This gateway class is much better IMHO.