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# multi-dimensional list using join

how to flatten a 2D list using join method?

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 i in range(len(musical_groups)):
for j in range(len(musical_groups[i])):
print(musical_groups[i][j] + ',')
```

What you're attempting may work in a real world situation, but not for the way this practice problem is set up. Also notice that you're printing only a comma, not a comma and a space. Using join is the more pythonic practice, shown below.

Part 1

```for group in musical_groups: #for each group in musical_groups
print(', '.join(group)) #print a string created by joining each element in the group
```

Part 2

```for group in musical_groups:
if len(group) == 3: #if and only if the group has 3 members (the list is length 3)
print(', '.join(group)) #print the joined string
```