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Python Introducing Lists Build an Application Multidimensional Musical Groups

Posted by Shannon Ferguson
Shannon Ferguson
1,221 Points

I am hung up on this question.

Here is a multi-dimensional list of musical groups. The first dimension is group, the second is group members.

Can you

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 item in musical_groups:
        print(", ".join(musical_groups[item]))

3 Answers

Travis Alstrand
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Travis Alstrand
Treehouse Project Reviewer
Travis Alstrand
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Travis Alstrand
Treehouse Project Reviewer

Hey there Shannon Ferguson ! Since we are already looping through each 'item' inside of musical_groups, we don't need to specify it's placement within that list. Just telling it to print the current 'item' it's looping across should do the trick :smiley:

for item in musical_groups:
    print(", ".join(item))
Asher Orr
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Asher Orr
Python Development Techdegree Graduate 9,410 Points
Asher Orr
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Asher Orr
Python Development Techdegree Graduate 9,410 Points

Hi Shannon! This is the syntax for the .join method:

string.join(iterable)

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 item in musical_groups:
        print(", ".join(musical_groups[item]))

In your current code, you're iterating through each item. That's your iterable- if you replace what's in the parentheses after join with item (your iterable), it should pass the challenge.

I hope this helps. Let me know if you have any questions!

Nicole Groenewald
Nicole Groenewald
1,031 Points
Nicole Groenewald
Nicole Groenewald
1,031 Points

When I do this code I get "Traceback (most recent call last): File"/home/treehouse/workspace/music.py", line 12 in <module> print(", ".joinmusical_groups[groups])) TypeError: list indices must be integers or slices, not list

Here's all my code, just in case

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 groups in musical_groups:
    print(", ".join(musical_groups[groups]))
Asher Orr
seal-mask
.a{fill-rule:evenodd;}techdegree seal-36
Asher Orr
Python Development Techdegree Graduate 9,410 Points
Asher Orr
.a{fill-rule:evenodd;}techdegree seal-36
Asher Orr
Python Development Techdegree Graduate 9,410 Points

When you enter this code:

for groups in musical_groups:

You are looping through each list within musical_groups. "groups" essentially means "each list within musical_groups."

Each list within musical_groups has several strings (the members of the band/group.) To pass the challenge, you need to join the strings together.

Remember, this is the syntax for the .join() method:

string.join(iterable)

for groups in musical_groups:
    string.join(iterable)

"groups" is your iterable.

    print(", ".join(musical_groups[groups]))

A list index can't be another list- that type of syntax doesn't work in Python. That's why you're getting the TypeError.

Does this answer your question?