prob_50.py

#!/usr/bin/env python3
# -*- coding: utf-8 -*-
"""
Created on Mon Feb 13 14:02:20 2017

@author: fun
"""

from timeit import default_timer as timer

start = timer()

def isprime(n):
    """Returns True if n is prime."""
    if n == 2:
        return True
    if n == 3:
        return True
    if n % 2 == 0:
        return False
    if n % 3 == 0:
        return False

    i = 5
    w = 2

    while i * i <= n:
        if n % i == 0:
            return False

        i += w
        w = 6 - w

    return True
 
def prime_list():
    """Create prime number list below 1000000"""
    L = []
    for n in range(1, 1000000):
        if isprime(n):
            L.append(n)
    return L
 
def add_primes(primes, switch):
    """Return the last number in the list (largest prime),
    and the in-loop counter (consecutive numbers)"""
    counter = switch # start with this prime number
    in_counter = 0
    sum = 0
    L = []
    while sum < 1000000:
        sum = sum + primes[counter]
        if isprime(sum):
            L.append(sum)
        in_counter += 1 # in loop counter
        counter += 1
    if L[-1] < 1000000:
        return L[-1], in_counter
    elif L[-1] > 1000000:
        print('***')
        return L[-2], in_counter
        
def main():
    """Main Program"""
    primes = prime_list()
    main_counter = 0
    for switch in range(0, 20):
        x = add_primes(primes, switch)
        print(x[0], x[1])
        if x[0] > main_counter:
            main_counter = x[0]
    print("Answer = ", main_counter)
             
if __name__ == '__main__':
    main()
    
end = timer()
time_taken = (end-start)*1000
print(time_taken)