Welcome to the Treehouse Community

Want to collaborate on code errors? Have bugs you need feedback on? Looking for an extra set of eyes on your latest project? Get support with fellow developers, designers, and programmers of all backgrounds and skill levels here with the Treehouse Community!

Looking to learn something new?

Treehouse offers a seven day free trial for new students. Get access to thousands of hours of content and join thousands of Treehouse students and alumni in the community today.

Start your free trial

Python Introducing Lists Build an Application Multidimensional Musical Groups

Min He
Min He
789 Points


for group in musical_groups: s = "," print(s.join(group))

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"],
    s = ","
    print(s.join(group))for group in musical_group

1 Answer

Chris Freeman
Chris Freeman
Treehouse Moderator 68,404 Points

Hey Min He, your solution is very cleaver!

With some modifications, I was able to get your code to produce the expected correct output. I needed to create separate lines instead of a list of strings.

s = ", "
print(s.join([", ".join(group) for group in 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

However, including the corrections doesn’t pass because the checker doesn’t like the unexpected variable s and is looking for a regular for loop and not a list comprehension.

Can you figure out how to get the same output using a regular for loop with the variable s?

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