Function goldbach

primelib/primelib.py:280–327

Goldbach's assumption input: a even positive integer 'number' > 2 returns a list of two prime numbers whose sum is equal to 'number'

(number)

def goldbach(number):
    """
    Goldbach's assumption
    input: a even positive integer 'number' > 2
    returns a list of two prime numbers whose sum is equal to 'number'
    """

    # precondition
    assert isinstance(number, int) and (number > 2) and isEven(number), (
        "'number' must been an int, even and > 2"
    )

    ans = []  # this list will returned

    # creates a list of prime numbers between 2 up to 'number'
    primeNumbers = getPrimeNumbers(number)
    lenPN = len(primeNumbers)

    # run variable for while-loops.
    i = 0
    j = 1

    # exit variable. for break up the loops
    loop = True

    while i < lenPN and loop:
        j = i + 1

        while j < lenPN and loop:
            if primeNumbers[i] + primeNumbers[j] == number:
                loop = False
                ans.append(primeNumbers[i])
                ans.append(primeNumbers[j])

            j += 1

        i += 1

    # precondition
    assert (
        isinstance(ans, list)
        and (len(ans) == 2)
        and (ans[0] + ans[1] == number)
        and isPrime(ans[0])
        and isPrime(ans[1])
    ), "'ans' must contains two primes. And sum of elements must been eq 'number'"

    return ans


# ----------------------------------------------