To find first N prime numbers in python

Question

I am new to the programming world. I was just writing this code in python to generate N prime numbers. User should input the value for N which is the total number of prime n

Answer 1

The line k = k-1 does not do what you think. It has no effect. Changing k does not affect the loop. At each iteration, k is assigned to the next element of the range, so any changes you have made to k inside the loop will be overwritten.

Answer 2

This is my version

import timeit
import math

__author__ = 'rain'


primes = [2]

def is_prime(n):
    for prime in primes:
        if n % prime == 0:
            return False
    return True


def find_nth_prime(n):
    current_index = 0
    while(len(primes) < n):
        if current_index == 0:
            start_value = 3
            end_value = 2 * 2
        else:
            start_value = primes[current_index - 1] * primes[current_index - 1] + 1
            end_value = primes[current_index] * primes[current_index]
        for i in range(start_value, end_value):
            if is_prime(i):
                primes.append(i)
        current_index += 1
    return primes[n-1]


def solve():
    return find_nth_prime(10001)

print solve()

print timeit.timeit(solve, number=10)

I use a sieve to scan primes, it's quite quick

It's take only 3.8e-06 seconds to get 10001th prime (10 times).

Answer 3

def Isprime(z):
    '''returns True if the number is prime OTW returns false'''
    if z<1:
        return False
    elif z==1:
        return False

    elif z==2:
        return True 

    else:
        for i in range(2,z):
            if z%i==0:
                return False
            else:
                return True

This is the way I did it. Of course, there are so many ways you can do it.

Answer 4

prime=2
counter = 0
x = int(input("Enter the number:\n"))
while (counter < x):
    if all(prime%j!=0 for j in range(2, prime)):
        print(prime, "is a prime number")
        counter+=1


    prime+=1

Answer 5

def isprime(n):
    if n <= 1:
        return False
    for x in range(2, n):
        if n % x == 0:
            return False
    else:
        return True

def list_prime(z):
    y = 0
    def to_infinity():
        index=0
        while 1:
            yield index
            index += 1
    for n in to_infinity():
        if y < z:
            if isprime(n):
                y = y + 1
                print(n, end='\n', flush=True)
        else:break
    print(f'\n {z} prime numbers are as above.')

# put your range below
list_prime(10)