Skip to main content
Showing results for 
Search instead for 
Did you mean: 

The ultimate Microsoft Fabric, Power BI, Azure AI & SQL learning event! Join us in Las Vegas from March 26-28, 2024. Use code MSCUST for a $100 discount. Register Now

New Member

Expand a list of various types into a new list

Trying to figure out how to programatically expand a list of various data types, including other lists. 


For example, here is a list of lists:




If I "drill down" to the next level using List.Combine, I now have more lists, and some text values:




The first List contained two Lists, the second List contained two text values.


Now I want to drill down again into those two list items, but I can't use List.Combine anymore, because that only works with data type List, and now I have some text values in my list. I want keep the text values as part of the new list, but continue drilling down into nested lists, until eventually I have a list of all text values. 


Any help would be greatly appreaciated! 

New Member

Thanks guys, I ended up using this function, works great!





View solution in original post

New Member

Thanks guys, I ended up using this function, works great!





Impactful Individual
Impactful Individual


You want is similar to {{"a", "b"}, {"c", "d"}, "e", "f", {"g", {"h", "i"}}} to convert to {"a", "b", "c", "d", "e", "f", "g", "h", "i"}?

Hi @shaunm001 

try this, a recursive function that keeps using List.Combine until all lists have been expanded. For illustration purposes, it uses the list created in Source = and you'll see the result in the last step

  expandFunc_ = (inputList_)=>
    step0 = List.Combine(List.Transform(inputList_, each if Value.Type(_) = type list then _ else {_})),
    step1 = List.Accumulate(inputList_, true, (state, current)=> state and Value.Type(current) <> type list  ),
    output = if step1 = true then step0 else @expandFunc_(step0) 
  Source = {{"a", "b"}, {"c", "d"}, "e", "f", {"g", {"h", {"i",{"j", "l", "m"}}}}},
  resfunc = expandFunc_(Source)


Please mark the question solved when done and consider giving kudos if posts are helpful.

Contact me privately for support with any larger-scale BI needs



Super User
Super User

Seems to me that you will need a new column where you make the decision to drill down or not based upon the data type. You could probably turn around and combine that into a single step in your M code.

@ me in replies or I'll lose your thread!!!
Instead of a Kudo, please vote for this idea
Become an expert!: Enterprise DNA
External Tools: MSHGQM
YouTube Channel!: Microsoft Hates Greg
Latest book!:
Mastering Power BI 2nd Edition

DAX is easy, CALCULATE makes DAX hard...

Helpful resources

Fabric Community Conference

Microsoft Fabric Community Conference

Join us at our first-ever Microsoft Fabric Community Conference, March 26-28, 2024 in Las Vegas with 100+ sessions by community experts and Microsoft engineering.

February 2024 Update Carousel

Power BI Monthly Update - February 2024

Check out the February 2024 Power BI update to learn about new features.

Fabric Career Hub

Microsoft Fabric Career Hub

Explore career paths and learn resources in Fabric.

Fabric Partner Community

Microsoft Fabric Partner Community

Engage with the Fabric engineering team, hear of product updates, business opportunities, and resources in the Fabric Partner Community.

Top Solution Authors
Top Kudoed Authors