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10.3 Nested Loops

Nested Loops

Nested loops are loops inside of loops. Now, why would we want loops inside of loops? It's because they help us create advanced functions that we can use to do cool things. We can run while and for loops inside of other while and for loops. Through these loops, we can develop an elaborate process that can help us sort and analyze data.

Traversing 2D Lists

You can also use nested for loops to traverse 2D (or multi-dimensional) lists:

# print each element in my_list
# and each element in the inner lists
for inner_list in my_list:
    print(inner_list)
    for word in inner_list:
        print(word)

View code on GitHub.

Let's step through this code. In the outer for loop, we are iterating through each element in my_list. Well, each element in my_list is a list itself. So, when we print inner_list, it'll print the current inner_list. Before it moves on to the next inner list, the inner for loop will iterate through each element in the inner list and print it.

Output:

['docs', 'slides', 'sheets']
docs
slides
sheets
['google', 'amazon', 'facebook']
google
amazon
facebook
['this', 'is', 'python']
this
is
python

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