如何在Python中求一定范围内的素数之和？

Question

我对 Python 和一般编程完全陌生，所以如果有人能够为初学者提供非常友好的帮助，那将会很有帮助。我正在尝试让素数之和达到 50。

我使用了下面的代码，但它在我的总和上增加了 2。例如，50 以内的素数之和应该是 326，但我得到 328 作为我的输出

upto = int(input("Find sum of prime numbers upto : "))

sum = 0

for num in range(2, upto + 1):

    
    for i in range(2, num):
        if (int(num % i) == 0):
            break;

    #If the number is prime then add it.
    else:
        sum += num

print("\nSum of all prime numbers upto", upto, ":", sum)

Answer 1

您的代码正在运行很好，“从1到50的素数之和”的答案是328而不是326，如果您仍然对此有疑问，您可以使用下面的代码检查您的结果：

说明：

给定一个范围[l, r]

，任务是找到该范围内所有素数的总和。

# from math lib import sqrt method
from math import sqrt

# Function to compute the prime number
def checkPrime(numberToCheck) :

    if numberToCheck == 1 :
        return False

    for i in range(2, int(sqrt(numberToCheck)) + 1) :

        if numberToCheck % i == 0 :
            return False

    return True

# Function to iterate the loop
# from l to r. If the current
# number is prime, sum the value
def primeSum(l, r) :

    sum = 0

    for i in range(r, (l - 1), -1) :

        # Check for prime
        isPrime = checkPrime(i)
        
        if (isPrime) :

            # Sum the prime number
            sum += i

    return sum





# Driver code   
if __name__ == "__main__" :

    l, r = 1, 50

    # Call the function with l and r
    print(primeSum(l, r))

我在上面的代码中设置了范围，只需将代码复制并粘贴到编辑器中并运行代码，您就会看到结果。

Answer 2

您需要处理两个部分。一是检查该数字是否是质数。其次是迭代数字范围。请参考下面的代码，

from math import sqrt

sum = 0
#some explanation here we are iterating from 50 all the way to 1. So you can indicate your range here. -1 is the step value which tells the difference between each iteration.
for i in range(50, 0, -1):

    # Check whether it is a prime number here
    bPrime = True  #initialize a boolean here to be indicated by the loop below
    for a in range(2, int(sqrt(i)) + 1):
        if i % a == 0:
            bPrime = False    #definitely not a prime,break the loop and set boolean to false
            break
        bPrime = True         #not ==0 so it is a prime, set boolean to true
        
    if (bPrime) :
        # Add up if it is a prime number
        sum += i
        
#view the results 
print(sum)

它应该给你328

Answer 3

50 以内的素数之和仅为 328，而不是 326。

但是，如果您想要前 50 个

奇数质数的总和，那么您可以对代码进行较小的更改，如下所示，这将为您提供 326 [这是范围 50 之前的奇数质数的总和]

upto = int(input("Find sum of prime numbers upto : "))

sum = 0

for num in range(3, upto+1):

    
    for i in range(2, num):
        if (int(num % i) == 0):
            break;

    #If the number is prime then add it.
    else:
        sum += num

print("\nSum of all prime numbers upto", upto, ":", sum)