Primality test for numbers of the form N=2*p+1

safeprime.py

# Author: Pedja 


from sympy import *

print("                        ***** SAFE PRIME *****\n\n\n")
while True:
	
    
   
    p=int(input("Enter a prime number : "))
  
	
    def test(p):
        if p%6==1:
            return "composite"
        elif pow(3,p,2*p+1)==1:
            return "prime"
        else:
            return "composite"
		
	
    if not(isprime(p)):
        print("Enter a prime number")
    elif p==2:
        print("2*"+str(p)+"+1 is prime")
    elif p==3:
        print("2*"+str(p)+"+1 is prime")
    else:
        print("2*"+str(p)+"+1 is "+test(p))
    
		
    try_again = ""
    # Loop until users opts to go again or quit
    while not(try_again == "1") and not(try_again == "0"):
        try_again = input("Press 1 to try again, 0 to exit. ")
        if try_again in ["1", "0"]:
            continue  # a valid entry found
        else:
            print("Invalid input- Press 1 to try again, 0 to exit.") 
    # at this point, try_again must be "0" or "1"
    if try_again == "0":
        break