4. Looping over a collection with indices

Use enumerate when you need both the index and the element.

enumerate keeps the element and its position tied together as one iteration concept. That is less fragile than indexing into the collection manually, especially if the loop body later changes.

4.1. Don’t do this

names = ['john', 'jane', 'jeremy', 'janice', 'joyce', 'jonathan']

for i in range(len(names)):
    print(i, names[i])

4.2. Do this

names = ['john', 'jane', 'jeremy', 'janice', 'joyce', 'jonathan']

for i, name in enumerate(names):
    print(i, name)