Prime factors of a number using Python

def prime_factors(n):
    i = 2
    factors = dict()
    while i * i <= n:
        if n % i:
            i += 1
        else:
            n //= i
            if i in factors:
                factors[i] += 1
            else :
                factors[i] = 1
    if n > 1:
        if n in factors:
            factors[n] += 1
        else :
            factors[n] = 1
    return factors