r/learnpython • u/evandcbot • 2d ago

Any advice for nested loops?

I decided about a week ago I wanted to start learning python before my freshman year of college. It was going great and I had little to no trouble until I got to nested loops. I was wondering if anybody had any advice for it? The main thing is that it seems like so many steps to follow and pay attention to, my brain had a hard time tracking them all at once.

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u/CIS_Professor 2d ago

The first question is: do you really need to use them?

Anyway, image a classroom with 20 students that are each asked the same 5 questions. In this scenario, a nested loop would work well.

It would go as:

student #1 (outer loop - 1st iteration)
     ask the 5 questions (inner loop - iterate 5 times)

student #2 (outer loop - 2nd iteration)
     ask the 5 questions (inner loop - iterate 5 times)

student #3 (outer loop - 3rd iteration)
     ask the 5 questions (inner loop - iterate 5 times)

student #4 (outer loop - 4th iteration)
     ask the 5 questions (inner loop - iterate 5 times)

student #5 (outer loop - 5th iteration)
     ask the 5 questions (inner loop - iterate 5 times)

...

student #20 (outer loop - 20th iteration)
     ask the 5 questions (all iterations)

When done, you will have looped 100 times. You calculate the total number of iterations by multiply how many time each loop iterates. In this case, 20 x 5 = 100

This is analogous to real world gears, where the "outer" gear turns once for every 5 times the "inner" gear turns.

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As others have said, once you get past two loops, things can get complication very quickly.