Lesson 3 of 4

Loops

Loops repeat code so you don't have to. A for loop runs once for each item in a sequence. range(3) gives you 0, 1, 2:

Try changing the range. range(1, 6) starts at 1 and stops before 6.

Building up a total

A common pattern is to start a variable at zero and add to it inside the loop:

while loops

A while loop keeps going as long as its condition is true:

Careful: if the condition never becomes false, the loop runs forever. Here that just means the sandbox stops it after a few seconds.

Exercise: Sum to N

Write sum_to(n) that returns 1 + 2 + ... + n.