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Python Introducing Lists Build an Application Multidimensional Musical Groups

Posted by Anthony Julian
Anthony Julian
Courses Plus Student 6,313 Points

How do I only show the groups of 3 in a multidimensional array?

Struggling with Introducing Lists, final code challenge task 2. How do I only show the groups with 3 members? (i.e. ["Ad Rock", "MCA", "Mike D."], ["Salt", "Peppa", "Spinderella"], ["Run", "DMC", "Jam Master Jay"])

Here is the code I have so far:

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 members in musical_groups:
    print(", ".join(members))
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"],
]
# Your code here
for members in musical_groups:
    print(", ".join(members))

1 Answer

Brandon White
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Brandon White
Full Stack JavaScript Techdegree Graduate 34,660 Points
Brandon White
.a{fill-rule:evenodd;}techdegree seal-36
Brandon White
Full Stack JavaScript Techdegree Graduate 34,660 Points

Hi Anthony,

If I were attempting to show only the groups of three members joined as a string, I would test if the length of the current list were three, and I would only join and print the lists that evaluated to true on those tests.

Anthony Julian
Anthony Julian
Courses Plus Student 6,313 Points

Thanks Brandon, however I ran an "if" statement and it didn't work. Please elaborate further? Thanks

Brandon White
.a{fill-rule:evenodd;}techdegree seal-36
Brandon White
Full Stack JavaScript Techdegree Graduate 34,660 Points

No problem. 

for members in musical_groups:
    print(", ".join(members))

The above is your code currently. Python loops through the musical _groups list and grabs every item (which is another/nested list) and prints it.

But if you don’t want it to print every list item/musical group, you could test:

for members in musical_groups:
    if len(members) == 3:
        print(", ".join(members))

This way during each iteration of the loop python says, are there only three items in this nested list (musical group)? If there are, it prints those members. If not, it skips the print function and starts on the next iteration of the loop.

Make sense now?

Anthony Julian
Anthony Julian
Courses Plus Student 6,313 Points

Thanks so much Brandon. I actually had that method correct, but had len(musical_groups) instead of len(members). Makes much more sense now. Cheers