How does Python reference modules within Excel?

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Calling Python code from within Excel, and the vast functionality it unlocks Part four of a five-part series of blogs
Excel and Python are getting ever more intertwined: you can now use the PY function to write (and call) Python code from within an Excel worksheet Writing Python code within an Excel workbook to fill cells Returning dataframes from Python code to fill Excel ranges Manipulating images in Python within Excel How does Python reference modules within Excel? (this blog) Creating and calling your own functions in Python

Calling Python code from within Excel, and the vast functionality it unlocks

Part four of a five-part series of blogs

Excel and Python are getting ever more intertwined: you can now use the PY function to write (and call) Python code from within an Excel worksheet

Writing Python code within an Excel workbook to fill cells
Returning dataframes from Python code to fill Excel ranges
Manipulating images in Python within Excel
How does Python reference modules within Excel? (this blog)
Creating and calling your own functions in Python

Posted by Andy Brown on 27 October 2025

In this blog

Which modules are installed by default
Importing additional modules
Some things aren't allowed

For this part of the blog I want to show why we haven't needed to reference any of the modules we've used (pandas, PIL, etc.), and how the Python virtual enviornment within Excel works.

Which modules are installed by default

To see what Excel includes by default when you insert Python, choose this option on the Formulas tab of the ribbon:

This option will show you the code which runs at the start of any Python program that you insert into Excel.

What you should then see is this in the Python editor sidebar:

This code runs in the background so that you have automatic access to Pandas, NumPy, MatPlotLib and Excel, among other modules, using the usual default aliases.

But surely this is not complete, as it doesn't include PIllow, and yet in the previous part of this blog I was able to work with the PIL library without importing it? I suspect that Excel does import the PIL module, but it's just not shown in this initialisation help feature.

Importing additional modules

Suppose you want to use the Python Faker module to generate a list of 5 random (made-up) females names:

Whenever you recalculate the worksheet this list should change.

You could do this with the Faker module, but you would have to install it otherwise you'd get this error:

If you try to reference a module which isn't imported, you'll see this error.

Here's what your Python code could look like for this example:

# import the necessary module

from faker import Faker

# create a faker session

fake = Faker()

# generate a list containing 5 names

fake_names = []

for number in range(5):

fake_names.append(fake.name_female())

# now show these names

fake_names

# note - could have done with single line comprehension

# [fake.name_female() for _ in range(5)]

Some things aren't allowed

Python within Excel uses a virtual environment in the cloud (at least, that's the way I choose to understand it). You can see which modules are available in this environment here:

This page warns you that you won't be able to do some things in Python (the link shown goes to this page).

So although (for example) you can import the requests module, you won't be able to use it to access a website:

This Python code would return 403, the HTTP status code meaning access to the requested resource is forbidden.

I don't think it's possible to call your own modules, as you'd somehow need to upload these first into Excel's virtual environment in the cloud, but you can call functions you've created, as shown in the final part of this blog.

Parts of this blog
Writing Python code within an Excel workbook to fill cells Returning dataframes from Python code to fill Excel ranges Manipulating images in Python within Excel How does Python reference modules within Excel? (this blog) Creating and calling your own functions in Python

Some other pages relevant to the above blogs include:

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Which modules are installed by default

Importing additional modules

Some things aren't allowed

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