P7.py

# -*- coding: utf-8 -*-
"""
Created on Sun Jun 25 22:02:06 2017

@author: 84338
"""
#质数生成算法

def eratosthenes(end, start=2, return_boolean=False):
    """
    Finds all primes < `end`.

    :param end: An integer. The upper limit of the range to look for primes.
    :param start: An integer. The start of the range to look for primes.
    :param return_boolean: A boolean. Represents the type of return type.
    :rtype: Depending on `return_boolean` either returns boolean and primes or
            just the primes.
    """
    primes = []
    if end < start or end < 2:
        return []
    is_prime = [True for i in range(end + 1)]
    is_prime[0] = is_prime[1] = False
    for i in range(2, end + 1):
        if not is_prime[i]:
            continue
        if start <= i <= end:
            primes.append(i)
        j = i * i
        while j <= end:
            is_prime[j] = False
            j += i
    if return_boolean:
        return primes, is_prime
    return primes