Python Python code for generating prime# list and evaluting a number

[mr.me]

Homework Statement

I am attempting to allow a user to enter a number and check to see if it is in a list of already generated prime numbers Here's my attempt

Where can I put the code to allow the number to be checked, the prime list generator works fine alone

def buildPrimeList ():
    
    primeList = [1, 2]
    possiblePrime = 3
    print "To calculate a list of prime values less than or equal a number..."

    x=int(raw_input("Enter a number higher then 3   "))
   
    while (possiblePrime <= x):  # changed input method
        divisor = 2
        isPrime = True
        y= int(raw_input("To see if a number is in the list enter that number enter -1 to exit: "))       
        while (divisor < possiblePrime ): #change condition to only less than possible prime
            if ((possiblePrime % divisor) == 0): 
                isPrime = False
          divisor = divisor + 1
        
        if (isPrime):
            primeList.append(possiblePrime)
            print primeList
            
        if y== -1:
            print "Goodbye"
            break
        if y in primeList:
            print y, "Is in the list"
        if y not in primeList:
            print y, "Is not in the list"    
                 
      possiblePrime = possiblePrime + 2
        
            
    return primeList
   
    
buildPrimeList()

 

[Dick]

Why are you asking them to enter a number to check if it's in the list before you are done building the list? Why don't you move the y stuff outside of the loop that builds the list?

 

[mr.me]

The user is supposed to be repeatedly prompted, that is why the y=raw_input is in the loop

 

[Dick]

It's still in the wrong place. Make a loop outside of buildPrimeList and put your input there.

 

[mr.me]

Thanks,

I did this and it works well enough, any general suggestions on the code

def buildPrimeList ():
    
    primeList = [1, 2]
    possiblePrime = 3
    print "To calculate a list of prime values less than or equal a number..."
    
    x=int(raw_input("Enter a number higher then 3   "))
    
    while  (possiblePrime <= x):  # for personal preference changed range to raw_input, so that the range can be arbitrary, though at a certain point a large range will consume a-lot of memory
        divisor = 2
        isPrime = True
              
        while (divisor < possiblePrime ):
            if ((possiblePrime % divisor) == 0): 
                isPrime = False
            divisor = divisor + 1
        if (isPrime):
            primeList.append(possiblePrime)
        
        possiblePrime = possiblePrime + 2
    while (primeList==primeList):   
        y= int(raw_input("To see if a number is in the list enter that number enter -1 to exit: "))    
        if y== -1:
            print "Goodbye"
            break
        if y in primeList:
            print y, "Is in the list"
        if y not in primeList:
            print y, "Is not in the list"
           
    return primeList