CODEWITHSUNDEEP
if-statementsumpython-3.6
Duncan Alf Zhang
Duncan Alf Zhang

Reputation: 37

Write a function that calculates the sum of all values in a list of integers that are both positive and even

The function should accept a single list as a parameter. The function should return an integer value as the result of calculation. If there are no positive and even integer values in the list, your function should return 0.

My current code:

def main():
    print (sum_positive_even([1,2,3,4,5]))
    print (sum_positive_even([-1,-2,-3,-4,-5]))
    print (sum_positive_even([1,3,5,7,9]))

def sum_positive_even(list):
    for num in list:
        if num < 0:
            list.remove(num)
    for num in list:
        if num % 2 == 1:
            list.remove(num)
    result = sum(list)
    return result

main()

The output should be like:

6
0
0

I'm confused where I should put the 'return 0'. Thanks TA!

Upvotes: 0

Views: 461

Answers (1)

perigon
perigon

Reputation: 2095

Deleting from a list while you iterate over it is a Bad Idea - it's very easy to get hard-to-track-down bugs that way. Much better would be to build a new list of the items you want to keep. You don't need a special case of returning 0; the general approach should be able to handle that.

Also, it's better not to use list as a variable name in Python, because that's the name of a built-in.

A modification of your approach:

def sum_positive_even(lst):
    to_keep = []
    for num in lst:
        if num > 0 and num % 2 == 0:
            to_keep.append(num)
    return sum(to_keep)

Since the sum of an empty list is 0, this covers the case where there are no positive even numbers.

Upvotes: 1

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