How to Find LCM in Python | Step-by-Step Tutorial

What is LCM? | Maths Explanation for Python Kids

Akin to finding H.C.F., L.C.M. is commonly found by repeated factorisation. Only this time, the factors do not have to be common amongst the set of numbers.

If we have the set of numbers 8, 12 and 18 for example, their L.C.M. is found thus:

Hence, L.C.M. of 8, 12 and 18 = 2 X 2 X 2 x 3 x 3 = 72

Step-by-Step Guide to L.C.M. by Factorisation in Python

We shall follow the steps below in writing our Python LCM code.

Step 1:

Do a numerical reverse sort on the (resulting) set so its first member is the largest in the set.

Step 2:

Starting with 2, iteratively check through the set of numbers for individual factors.

Step 3:

For each individual factor, divide affected member(s) of the number set by the factor.

Step 4:

Repeat the above steps recursively until there are no more individual factors.

Create a new Python class file; File, New File.
Call it FindLCM.py

Type out the adjoining Python code for finding Lowest Common Multiple (L.C.M.)

Note: You can comment out the Python code for the main class from the previous lesson if you have been following.

So! Python Fun Practice Exercise - Find LCM

As a fun practice exercise, feel free to try out your own numbers, and see how the Python code finds the LCM of those numbers.

Python Code for Find LCM - Module File.

# A class
class findLCM:
    # A constructor
    def __init__(self, group):
        self.set_of_numbers = []
        for member in group:
            self.set_of_numbers.append(member)
        # Sort array in descending order
        self.set_of_numbers.sort(reverse=True)

        self.all_factors = []

        self.index = 1
        self.state_check = False
        self.calc_result = 1


    def findLCMFactors(self):
        #  Copy 'set_of_numbers' into 'arg_copy'
        self.arg_copy = []
        for number in self.set_of_numbers:
            self.arg_copy.append(number)
        # STEP 1:
        # sort in descending order
        self.arg_copy.sort(reverse=True)

        while self.index <= self.arg_copy[0]:
            self.state_check = False
            for count in range(len(self.set_of_numbers)):
                if self.set_of_numbers[count] % self.index == 0:
                    # STEP 3:
                    self.set_of_numbers[count] /= self.index
                    if self.state_check == False:
                        self.all_factors.append(self.index)

                    self.state_check = True # do not store the factor twice

            # STEP 4:
            if self.state_check: return self.findLCMFactors()

            self.index += 1

        return None


    # Returns an array reference of the desired set of even numbers
    def getLCM(self):
        # STEP 2:
        self.index = 2
        self.findLCMFactors()

        # iterate through and retrieve members
        for factor in self.all_factors:
            self.calc_result *= factor

        return self.calc_result

Python Code for Find LCM - Main Class.

#!/usr/bin/python
from LCM import findLCM

# Use the LCM module/class
group = [2, 3, 4]
lcm = findLCM(group)
answer = lcm.getLCM()
print("The L.C.M. of ", group, " is", answer, "\n")

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