User:Kithira/Course Pages/CSCI 12/Assignment 2/Group 1/Homework 2

Finding Prime Factors Using Python

Here is a program written in Python (programming language) that allows the user to input any positive integer and receive a list of the prime factors:

from Factors import Factor
from PrimeNumber import Prime 

def PrimeFactor(N): 
   M = [] 
   for L in Factor(N): 
       if Prime(L): 
           M.append(L) 
   return M 

def _test():
   assert( PrimeFactor(6) == [2,3] ) 
   print "Enter a number greater than 1 to find its prime factors: " 
   T = int( raw_input() ) 
   print "The prime factors of", T, "are:", PrimeFactor(T) 

if __name__ == '__main__': 
   _test()

Using Factor( ), the program goes through each factor of the designated number and checks if it is prime, using Prime( ). If True, the factor is added to the M list, then once all digits have been checked it returns the final list. Before allowing the user to input a number, it tests an input of 6 automatically to ensure any changes have not affected its functionality.

The code above relies upon the usage of existing programs to (1) find the factors and (2) check if a number is prime, which the user can provide themselves (if they have already written their own). To do this simply change the from file and the import module. Below are a couple examples of possible programs:

Factors

Returns a list of all the factors of a number.

def Factor(X):
    result = []
    n = 1
    while n <= X:
        if (X/n)*n == X:
            result.append(n)
            n += 1
        else:
            n += 1
    return result

Prime

Returns a boolean (True/False) of whether a number is prime.

from Factors import Factor

def Prime(X):
    return bool( len( Factor(X) ) == 2 )

This code relies upon the structure of the Factors program above, using the fact that the factors of a prime number are always 1 and itself.

Comments from Group 3

You have made a successful program that does what it sets out to do. However, you made no comments throughout your program. We also failed to comment our code however realize the importance of this tool. It may seem useless in the immediate future seeing as you will be able to remember why your code is the way that it is. However, when writing longer programs, commenting becomes important when one is trying to follow the logic of the code. It is also a tremendous amount of help when looking at code completed in the past (anywhere from a few days to a few years) and trying to remember the logic of the code then. Aside from this one error, your program is great!