Python Program to Print Prime Numbers in a Range

hardNested loopsPython

This combines two ideas: a loop over a range of numbers, and the prime check for each one.

The question

Read two integers a and b (one per line, a < b) and print every prime number from a to b (both included), separated by spaces.

The code

program.py

a = int(input())
b = int(input())
for n in range(max(a, 2), b + 1):
    for i in range(2, int(n ** 0.5) + 1):
        if n % i == 0:
            break
    else:
        print(n, end=" ")
print()

Try it Yourself »

Input

44
65

Output

47 53 59 61

How it works

1The outer loop goes through every number n from a to b. max(a, 2) skips 0 and 1, which are not prime.
2The inner loop tries divisors up to √n and breaks as soon as one divides n.
3The else of the inner loop runs only when no divisor was found — then n is printed.

Common mistakes

Printing 1 as a prime number.
Placing print(n) inside the inner loop, which prints the same number many times.

Now solve a similar question yourself

A new Python question every time, checked instantly.

Practice questions

More in Nested loops

Previous Next