Solution

Full Code

even_numbers = []
for i in range(1, 21):
    if i % 2 == 0:
        even_numbers.append(i)
print(even_numbers)

Quick Explanation

This loop goes from 1 to 20 and adds every even number to the list using the % 2 == 0 condition. Note that we use 21 as the upper bound of the range.

Finally, after exiting the look, we print out the result.