for and while loops

A for loop runs once for each item in a collection. It's the workhorse of row-by-row processing.

python

amounts = [499, 1299, 250]

total = 0

for a in amounts:

    total += a

print(total)

for i, a in enumerate(amounts):

    print(i, a)

OUTPUT

2048 0 499 1 1299 2 250

range(n) gives the numbers 0 to n-1. while repeats as long as a condition stays True, which you'll mostly see in retry loops. break exits a loop early and continue skips to the next item.

python

attempts = 0

while attempts < 3:

    attempts += 1

    print("connecting, attempt", attempts)

OUTPUT

connecting, attempt 1 connecting, attempt 2 connecting, attempt 3