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sh3nk
Write python code to display the prime factors of any user given number
I would start with the highest prime that is close to half of the number and work down. Also, you might want to check if it is prime right off.
These were from a couple of years back, but should still work. def makeprimelist(bound): max_ndx = (bound - 1) / 2 sieve = [True] * (max_ndx + 1) for ndx in range(int(bound ** 0.5) / 2): if sieve[ndx]: num = ndx * 2 + 3 sieve[ndx+num:max_ndx:num] = [False] * ((max_ndx-ndx-num-1)//num + 1) return [2] + [ndx * 2 + 3 for ndx in range(max_ndx) if sieve[ndx]] def factors(x,unique=0): if x ==1:return [1] pl = makeprimelist(x) tmp = x factors=[] while tmp > 1: for p in pl: if tmp%p==0: factors.append(p) tmp=tmp/p if unique: factors.sort() i=0 while i < len(factors)-1: if i < len(factors) and factors[i]==factors[i+1]: factors.remove(factors[i]) factors[i]=factors[i]*factors[i] else: i+=1 return factors
and i make no claims that that is the best way to implement either of the functions just the ones i used when i was learning python and playing on projecteuler.net