function return None after execution of a function

Question

I have this code to split a DNA strand into groups of 3. Everything in the result is intended except for that last "None"

def codons(x):
    for i in range(0, len(x), 3):
        result = print(x[i:i + 3])
    return result

When using with

print(codons('ATGCTCAAGTAGR'))

Returns:

ATG
CTC
AAG
TAG
R
None

This is why I never teach people about `print` too early. If the console is the only output device used in teaching, people tend to miss the difference between printing something and returning something, because ultimately all results are printed anyway. — Alexander, May 29 '21 at 21:23
Does this answer your question? [How is returning the output of a function different from printing it?](https://stackoverflow.com/questions/750136/how-is-returning-the-output-of-a-function-different-from-printing-it) — mkrieger1, May 29 '21 at 21:51

score 0 · Accepted Answer · answered May 29 '21 at 21:39

0

You can save the result in a list

 def codons(x):
        result=[]
        for i in range(0, len(x), 3):
            result.append(x[i:i + 3])
        return result

answered May 29 '21 at 21:39

Alan

score -1 · Answer 2 · answered May 29 '21 at 21:21

-1

Everything is right, just get rid of the return and the print when calling the function.

def codons(x):
    for i in range(0, len(x), 3):
        print(x[i:i + 3])
codons('ATGCTCAAGTAGR')

answered May 29 '21 at 21:21

Buddy Bob

2 Answers2