如何计算给定范围内的素数总数

Question

我试图找到一个范围内的素数（输入将由用户决定）和素数的总数。

我能找到质数，但无法完成计算质数的部分。谁能帮我？这是程序

#!/usr/bin/env python
import math

lower=input("lower value:")
upper=input("upper value:")
print("prime numbers between", lower,"and", upper, "are:")
for num in range (lower, upper+1):
 if num>1:
  for i in range (2,num):
   if num % i==0:
    break
  else: print(num)
def  count_prime(num,lower,upper):
  count_prime= 0
  for x in num:
    if lower <= x <= upper:
      count_prime += 1
print ( "count_prime:",count_prime )

结果输出如下（范围在10到100之间）

('prime numbers between', 10, 'and', 100, 'are:') 11 13 17 19 23 29 31 37 41 43 47 53 59 61 67 71 73 79 83 89 97 ('count_prime:', )

Answer 1

最简单的方法是让一个变量在您每次找到素数时递增。因此，当您打印数字时，还要将该计数加一。您可以通过其他各种方式来做到这一点，即通过将每个素数保存在一个数组中然后计算元素的数量等。

与变量有关：

lower=input("lower value:")
upper=input("upper value:")
count = 0
print("prime numbers between", lower,"and", upper, "are:")
for num in range (lower, upper+1):
 if num>1:
  for i in range (2,num):
   if num % i==0:
    break
  else: 
    print(num)
    count += 1
print ( "count_prime:", count )

与数组有关：

lower=input("lower value:")
upper=input("upper value:")
array = []
print("prime numbers between", lower,"and", upper, "are:")
for num in range (lower, upper+1):
 if num>1:
  for i in range (2,num):
   if num % i==0:
    break
  else: 
    print(num)
    array.append(num)
print ( "count_prime:", len(array))

Answer 2

要计算质数的个数，可以先用一个列表存储质数，然后直接用len求出质数的个数。这个很容易理解：

import math
store = []
lower=int(input("lower value:"))
upper=int(input("upper value:"))
print("prime numbers between", lower,"and", upper, "are:")
for num in range (lower, upper+1):
 if num>1:
  for i in range (2,num):
   if num % i==0:
    break
  else: 
    print(num)
    store.append(num)
print("The number of prime numbers are:",len(store))

Answer 3

"sympy" 图书馆在这些情况下会很有帮助

import sympy
lower=int(input("lower value:"))          #let it be 30
upper=int(input("upper value:"))          #let it be 60
l=list(sympy.primerange(lower,upper+1))   #[31,37,41,43,47,53,59]
z=len(l)
print(z)

Answer 4

我找到了一些其他方法来计算在中找到的素数这个例子你可以自定义你的列表。

def is_prime(n):
    if n <= 1:          # negative numbers, 0 or 1
        return False
    if n <= 3:          # 2 and 3
        return True
    if n % 2 == 0 or n % 3 == 0:
        return False

    for i in range(5, int(math.sqrt(n)) + 1, 2):
        if n % i == 0:
            return False

    return True



ans = [i for i in input().split() if is_prime(int(i))]
print(len(ans))

或者，如果您想在范围内完成相同的任务，则只需编辑 input().split() 到 range(lower,upper+1)

ans = [i for i in range(lower,upper+1) if is_prime(i)]
print(len(ans))

如何计算给定范围内的素数总数

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