zip is a built-in function that takes two or more sequence and ‘zips’ them into a list of tuples, where each tuple contains one element from each sequence.

The result is a list of tuples where each tuple contains a character from the string and the corresponding element from the list. If the sequences are not the same length, the result gets the length of the shorter one. You can use tuple assignment to traverse a list of tuples:

If you combine zip, for and tuple assignment, you get a standard idiom for traversing two (or more) sequences at the same time. For example, has_match takes two sequences, t1 and t2, and returns True if there is an index i such that t1[i] == t2[i]:

If you need to traverse the elements of a sequence and their indices, you can use the built-in function enumerate:

from Thinking in Python