1.4 Conditionals and Loops | Code Scholars Tutoring

How it works

Indentation defines blocks, so structure is enforced by layout. A for loop iterates over a sequence directly rather than over indices.

Iterate over items when the index is not needed, and enumerate when it is.

Looping over a range of indices out of habit, which is longer and easier to get wrong than iterating directly.

Python

total = 0
for value in range(1, 6):
    if value % 2 == 0:
        total += value
print(total)

Output

range stops before its upper endpoint. The conditional selects 2 and 4, whose sum is 6.

Determine the exact output and explain the state changes.

Python

n = 1
while n < 10:
    n *= 2
print(n)

Show solution

Output

The successive values are 2, 4, 8, 16. The next condition check ends the loop.

Create and print the list of odd integers from 1 through 7.

Show solution

Use a stepped range whose stop excludes 8.

One valid solution

odds = list(range(1, 8, 2))
print(odds)

Expected output

[1, 3, 5, 7]