Python for loops output into list

Question

def factors(n):
for i in reversed(range(1, n+1)):
    if n % i ==0:
        print(i)

This code currently outputs the factors of a number in a new line ex. factors(18) outputs 18 9 6 etc.... How can I make it so when I type

print("factors for 18 are:", factors(18))

Returns a list of

factors of 18: [18,9,6,3,2,1]

Without having print(i) in my function.

So basically your question is just "how do I create a list of numbers instead of printing the numbers"? Do you know about the return statement? — Aran-Fey
– Aran-Fey, Commented Sep 22, 2018 at 21:26
BTW, this algorithm is ok for small n, but it gets pretty slow for large n. A simple way to improve it is to save pairs of factors, i and n//i. So if n is a million, you only have to test i upto 1000. — PM 2Ring
– PM 2Ring, Commented Sep 22, 2018 at 21:36

PM 2Ring · Accepted Answer · 2018-09-22 21:38:04Z

2

def factors(n):
  ret = [] #Make an empty array to store number factors
  for i in reversed(range(1, n+1)):
    if n % i ==0:
      ret.append(i) #append factors
  return ret #return array of factors

print("Factors of 18", factors(18))

edited Sep 22, 2018 at 21:38

PM 2Ring

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answered Sep 22, 2018 at 21:26

cymruu

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1 Comment

Dan Osmith Over a year ago

I may be doing something wrong but when I run this program I get Factors of 18 [18]

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