Combining two LIsts in a unique way in Python

Question

I am working on a Project Euler 5 issue and use the following:

def findLCM(k): start=time.time() primes=[2,3,5,7,11,13,17,19,23] factors=[] for factor in range(2,k): if factor in primes: factors.append(factor) else: factorization=[] while factor!=1: for prime in primes: lastFactor=prime if factor%prime==0: factor/=prime factorization.append(lastFactor) break tmpFactors=[] for tmpFactor in factorization: if tmpFactor not in factors: factors.append(tmpFactor) else: tmpFactors.append(tmpFactor) factors.remove(tmpFactor) for tmpFactor in tmpFactors: factors.append(tmpFactor) print factors product=1 for factor in factors: product*=factor factors.sort() end=time.time() fnTime=end-start return product, fnTime, factors 

Is there a Python function with which I can combine factorization and factors such as this function? For example, if factors=[2, 3, 5] and factorization=[2, 2, 3] , the combined list should be [2, 2, 3, 5] .

Answer 1

The terminology is "the union of multisets .

It is implemented in Python using collections.Counter :

 >>> from collections import Counter >>> combined = Counter([2, 3, 5]) | Counter([2, 2, 3]) >>> list(combined.elements()) [2, 2, 3, 5]