Why is this for loop giving me an incorrect output?

Question

I have a function that tells me the factors of a number, then should print how many it has.

factors = 0
def getFactors(n):
 global factors
 for i in range(1,n):
 if n%i==0:
 print(i)
 factors += 1
 print(n, "has", factors, "factors.")

However, the number of factors seems to be wrong. Apparently 16 has 6 factors even though it clearly lists 4.

>>> getFactors(16)
1
2
4
8
16 has 6 factors.
>>> 

What have I done wrong here?

• Psytho: You don't need to go the whole way to n. Obviously, a factor cannot be greater than n/2. Thus you can spare a half of iterations with range(1, n/2)

Answer 1

On the first time you call getFactors(16) you will correctly get 4. The problem is likely that you've called the function multiple times, and since you used global factors, the value of factors isn't reset to 0 each time you call the function. The global variable keeps being mutated each time you call the function.

If you remove the global variable and make it function local it will work fine

def getFactors(n):
 factors = 0
 for i in range(1,n):
 if n%i==0:
 print(i)
 factors += 1
 print(n, "has", factors, "factors.")
>>> getFactors(16)
1
2
4
8
16 has 4 factors.

• user4487002: Brilliant. Thanks, I completely forgot it needed to be reset.
• Pynchia: @Eddie If instead of printing the factors you want to return them, you can turn the function to one line as return [i for i in range(1,n) if n%i == 0] (or use yield, of course)