3 · Work with collections · 10 MIN

Repeat with a loop

A loop applies an operation to each item.

for n in values visits each value. Keep an accumulator outside the loop so it survives every iteration. Use consistent indentation. Summing n numbers takes O(n) time and O(1) extra space.

Count the coins in a jar by adding each coin to a running total.

Read the example

total = 0
for n in [2, 3, 4]:
    total = total + n
print(total)

9

Your challenge

Return the sum of all numbers in input. An empty list sums to zero.

Common trap

Resetting total inside the loop loses earlier additions.