Showing results for 
Search instead for 
Did you mean: 

Fabric is Generally Available. Browse Fabric Presentations. Work towards your Fabric certification with the Cloud Skills Challenge.

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

PBI November 2023 Update Carousel

Power BI Monthly Update - November 2023

Check out the November 2023 Power BI update to learn about new features.

Community News

Fabric Community News unified experience

Read the latest Fabric Community announcements, including updates on Power BI, Synapse, Data Factory and Data Activator.

Dashboard in a day with date

Exclusive opportunity for Women!

Join us for a free, hands-on Microsoft workshop led by women trainers for women where you will learn how to build a Dashboard in a Day!

Power BI Fabric Summit Carousel

The largest Power BI and Fabric virtual conference

130+ sessions, 130+ speakers, Product managers, MVPs, and experts. All about Power BI and Fabric. Attend online or watch the recordings.

Top Solution Authors