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Python Introducing Lists Build an Application Multidimensional Musical Groups

Posted by matthew mahoney
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matthew mahoney
Python Development Techdegree Student 2,536 Points

Now I'd like to see only groups that are trios, you know 3 members. So can you please only print out the trios?

Hey there, Having a bit of a struggle with this one. I thoroughly watched the videos and must have missed this concept. Can someone help me get it right and explain what's happening in the right code? Thanks!

groups.py 
musical_groups = [
    ["Ad Rock", "MCA", "Mike D."],
    ["John Lennon", "Paul McCartney", "Ringo Starr", "George Harrison"],
    ["Salt", "Peppa", "Spinderella"],
    ["Rivers Cuomo", "Patrick Wilson", "Brian Bell", "Scott Shriner"],
    ["Chuck D.", "Flavor Flav", "Professor Griff", "Khari Winn", "DJ Lord"],
    ["Axl Rose", "Slash", "Duff McKagan", "Steven Adler"],
    ["Run", "DMC", "Jam Master Jay"],
]
for band in musical_groups:
    seperator = ", "
    bands = seperator.join(band)
    if len(bands) == 3:
        print(bands)

2 Answers

Chris Freeman
MOD
Chris Freeman
Treehouse Moderator 68,441 Points
Chris Freeman
Chris Freeman
Treehouse Moderator 68,441 Points

You are very close!! If you join the band members into a string before the len() check, you are checking the length of the string, which is almost certainly not 3 characters.

Post back if you need more help. Good luck!!!

Peter Vann
Peter Vann
36,427 Points
Peter Vann
Peter Vann
36,427 Points

Hi Matthew!

Join syntax is a little backwards from how you would do it in, say, Javascript.

This passes task 1:

musical_groups = [
    ["Ad Rock", "MCA", "Mike D."],
    ["John Lennon", "Paul McCartney", "Ringo Starr", "George Harrison"],
    ["Salt", "Peppa", "Spinderella"],
    ["Rivers Cuomo", "Patrick Wilson", "Brian Bell", "Scott Shriner"],
    ["Chuck D.", "Flavor Flav", "Professor Griff", "Khari Winn", "DJ Lord"],
    ["Axl Rose", "Slash", "Duff McKagan", "Steven Adler"],
    ["Run", "DMC", "Jam Master Jay"],
]
# Your code here
for band in musical_groups:
    if len(band) == 3: # you want to test the length of each "band list", and only include the ones with 3 members
        print( ", ".join(band) )

More info:

https://www.w3schools.com/python/ref_string_join.asp

I hope that helps.

Stay safe and happy coding!