Yes, runtime on this solution will be n^2 since they are entering every number 1 by 1 and it's an N * N table which means N^2 items will need to be entered.

apparently "best practice" is just, "shortest code"

You know it doesn't kill to have a few more lines? Bad practice.

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you're wrong, they're taking every letter in the alphabet it test it against s, if the letter is not in s, which mean it's not a pangram, which mean it would return False and the code ends there. However, if we iterate through the whole alphabet with every letter in s, the loops finish and it return True.