First prime number in python assignment expert

Answer to Question #245119 in Python for Raju

First Prime Number

You are given N inputs. Write a program to print the first prime number in the given inputs.

n = int(input("Enter number of integers: "))
numbers = []


for i in range(n):
    number = int(input("Enter number: "))
    isPrime=True
    if number > 1:
        for j in range(2, number):
            if (number % j) == 0:
                isPrime=False
                break
        if isPrime==True:
            numbers.append(number)
                
print("The first prime number in the given inputs is: "+str(numbers[0]))

Learn more about our help with Assignments: Python

First Prime Number

You are given N inputs. Write a program to print the first prime number in the given inputs.

Input

The first line of input is an integer N. The next N lines each contain an integer. Explanation

In the given example of

5 integers

1

10

4

3

2

The output should be

3.

Sample Input 1

5

1

10

4

3

2

Sample Output 1

3

Sample Input 2

4

2

3

5

7

Sample Output 2

2

n = int(input("Enter a positive integer: "))


is_primes = []  # list of potential prime numbers(contains primes and non primes)


for count in range(n):
    read = int(input("> "))
    is_primes.append(read)


non_primes = []


for num in is_primes:


    if num == 2 or num == 3:
        pass
    else:
        for i in range(2, num):
            if num % i == 0:
                non_primes.append(num)
                break
            else:
                pass


            
print(sum(non_primes))

Learn more about our help with Assignments: Python

For reference, there's a pretty significant speed difference between the various stated solutions. Here is some comparison code. The solution pointed to by Lennart is called "historic", the one proposed by Ants is called "naive", and the one by RC is called "regexp."

from sys import argv
from time import time

def prime(i, primes):
    for prime in primes:
        if not (i == prime or i % prime):
            return False
    primes.add(i)
    return i

def historic(n):
    primes = set([2])
    i, p = 2, 0
    while True:
        if prime(i, primes):
            p += 1
            if p == n:
                return primes
        i += 1

def naive(n):
    from itertools import count, islice
    primes = (n for n in count(2) if all(n % d for d in range(2, n)))
    return islice(primes, 0, n)

def isPrime(n):
    import re
    # see http://tinyurl.com/3dbhjv
    return re.match(r'^1?$|^(11+?)\1+$', '1' * n) == None

def regexp(n):
    import sys
    N = int(sys.argv[1]) # number of primes wanted (from command-line)
    M = 100              # upper-bound of search space
    l = list()           # result list

    while len(l) < N:
        l += filter(isPrime, range(M - 100, M)) # append prime element of [M - 100, M] to l
        M += 100                                # increment upper-bound

    return l[:N] # print result list limited to N elements

def dotime(func, n):
    print func.__name__
    start = time()
    print sorted(list(func(n)))
    print 'Time in seconds: ' + str(time() - start)

if __name__ == "__main__":
    for func in naive, historic, regexp:
        dotime(func, int(argv[1]))

The output of this on my machine for n = 100 is:

naive
[2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97, 101, 103, 107, 109, 113, 127, 131, 137, 139, 149, 151, 157, 163, 167, 173, 179, 181, 191, 193, 197, 199, 211, 223, 227, 229, 233, 239, 241, 251, 257, 263, 269, 271, 277, 281, 283, 293, 307, 311, 313, 317, 331, 337, 347, 349, 353, 359, 367, 373, 379, 383, 389, 397, 401, 409, 419, 421, 431, 433, 439, 443, 449, 457, 461, 463, 467, 479, 487, 491, 499, 503, 509, 521, 523, 541]
Time in seconds: 0.0219371318817
historic
[2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97, 101, 103, 107, 109, 113, 127, 131, 137, 139, 149, 151, 157, 163, 167, 173, 179, 181, 191, 193, 197, 199, 211, 223, 227, 229, 233, 239, 241, 251, 257, 263, 269, 271, 277, 281, 283, 293, 307, 311, 313, 317, 331, 337, 347, 349, 353, 359, 367, 373, 379, 383, 389, 397, 401, 409, 419, 421, 431, 433, 439, 443, 449, 457, 461, 463, 467, 479, 487, 491, 499, 503, 509, 521, 523, 541]
Time in seconds: 0.00515413284302
regexp
[2, 3, 5, 7, 11, 13, 17, 19, 23, 29, 31, 37, 41, 43, 47, 53, 59, 61, 67, 71, 73, 79, 83, 89, 97, 101, 103, 107, 109, 113, 127, 131, 137, 139, 149, 151, 157, 163, 167, 173, 179, 181, 191, 193, 197, 199, 211, 223, 227, 229, 233, 239, 241, 251, 257, 263, 269, 271, 277, 281, 283, 293, 307, 311, 313, 317, 331, 337, 347, 349, 353, 359, 367, 373, 379, 383, 389, 397, 401, 409, 419, 421, 431, 433, 439, 443, 449, 457, 461, 463, 467, 479, 487, 491, 499, 503, 509, 521, 523, 541]
Time in seconds: 0.0733318328857

As you can see, there's a pretty big discrepancy. Here it is again for 1000 (prime outputs removed):

naive
Time in seconds: 1.49018788338
historic
Time in seconds: 0.148319005966
regexp
Time in seconds: 29.2350409031

How do I find the first prime number in Python?

How do you print the first prime number in inputs Python?

What is the code for prime number in Python?

What is first prime number?