def eratosthenes(n):
    """
    This function is titled eratosthenes(n) because it uses the Eratosthenes Sieve to produce a list of prime
    numbers.  It takes in one positive integer arguement, the returns a list of all the primes less than the 
    given number.
    
        Args:
            n (int): User input
        Returns:
            primes (list): List of prime numbers less than the user input
    """
    primes = []
    
    #checks for positive number
    if n<=0:
        print("Please enter a positive number")
        return
    
    #creates list of numbers up to n
    count = 2
    while count<=n-1:
        primes.append(count)
        count +=1
        
    p = 2
    
    #starts with 2, then removes all multiples of 2.  Moves to 3, removes
    #all multiples of 3, and so on until we have a list of prime numbers 
    #less than n.
    while p<=n:
        for i in range(2, n+1):
            if i*p <= n:
                #checks to see if the number was already removed from the list
                if i*p not in primes:
                    continue
                else:
                    primes.remove(i*p)
        p +=1
    
    return primes