Why there is "none" when i try to count odd numbers?

Question

what i want:

count odd numbers of list a

my code as following:

def find_it(seq):
    set_seq=set(seq)
    dict_seq = {}
    for item in set_seq:
        dict_seq.update({item:seq.count(item)})
    print(dict_seq)

a=[20,1,-1,2,-2,3,3,5,5,1,2,4,20,4,-1,-2,5]
print(find_it(a))

This outputs:

{1: 2, 2: 2, 3: 2, 4: 2, 5: 3, 20: 2, -2: 2, -1: 2}
None

Why does it output None?

Are you missing a `return` statement in that function? The program is outputting the result of calling the function, and since it doesn't have a `return` statement, the result is `None`. — Lasse V. Karlsen, Nov 08 '18 at 07:22
thank you so much!!!how can i give the thumbs-up to you on website?i'm not familar on stackover... — CZ_want2b, Nov 08 '18 at 07:29

score 0 · Answer 1 · answered Nov 08 '18 at 07:26

0

You do not return anything so there is nothing to be print. Here is the answer yo are looking for!!

def find_it(seq):
    set_seq=set(seq)
    dict_seq = {}
    for item in set_seq:
        dict_seq.update({item:seq.count(item)})
    return dict_seq

a=[20,1,-1,2,-2,3,3,5,5,1,2,4,20,4,-1,-2,5]
my_dict = find_it(a)
print(my_dict)

answered Nov 08 '18 at 07:26

Anagnostou John

498
5
14

why `my_dict = find_it(a)`, why not just `print(find_it(a))` – dejanmarich Nov 08 '18 at 07:28
just for visual purposes! in order to show you that from the function find_it something is returned and afterwords you can do anything with it – Anagnostou John Nov 08 '18 at 07:29

score 0 · Answer 2 · answered Nov 08 '18 at 07:32

Counting the odd numbers

To count the odd numbers, after reducing to a set you should run the a loop looking at %2 append that number to a list (or increment a counter). Since you seem to be fairly new, here's an easy to understand approach:

def find_it(seq):
    set_seq=set(seq)
    odds=[]
    for item in set_seq:
        if item%2==1:
            odds.append(item)
    return len(odds)

Why there is "none" when i try to count odd numbers?

2 Answers2

Counting the odd numbers