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Python

Posted by Hussein Amr
Hussein Amr
2,461 Points

Returning True or False instead of the list

Let’s say I give you a list saved in a variable: a = [1, 4, 9, 16, 25, 36, 49, 64, 81, 100]. Write one line of Python that takes this list a and makes a new list that has only the even elements of this list in it.

a = [1, 4, 9, 16, 25, 36, 49, 64, 81, 100] b = [num % 2 == 0 for num in a]

print(b)

why does this only return "True" or "False" but not the numbers themselves?

1 Answer

Rich Zimmerman
Rich Zimmerman
24,063 Points

You want to create b like this:

b = [num for num in a if num % 2 == 0]

This way it will iterate over the numbers in a and only add them to b if num % 2 == 0

Hussein Amr
Hussein Amr
2,461 Points

Thank you. Can you elaborate the difference between this line and mine though?

Rich Zimmerman
Rich Zimmerman
24,063 Points

The way you have it, it's iterating over a and just checking if each num % 2 == 0, and returning the boolean value. Think of its this way...

for num in a:
    return num % 2 == 0

where you can think of the way i wrote it as:

for num in a:
    if num % 2 == 0:
        b.append(num)
return b