I am currently using a function that accepts two numbers and uses a loop to find the least common multiple of those numbers,

``````def lcm(x, y):
"""This function takes two
integers and returns the L.C.M."""

# Choose the greater number
if x > y:
greater = x
else:
greater = y

while(True):
if((greater % x == 0) and (greater % y == 0)):
lcm = greater
break
greater += 1

return lcm
``````

Is there a built-in module in Python that does it instead of writing a custom function?

### In Python 3.8 and earlier

There is no such thing built into the stdlib.

However, there is a Greatest Common Divisor function in the `math` library. (For Python 3.4 or 2.7, it’s buried in `fractions` instead.) And writing an LCM on top of a GCD is pretty trivial:

``````def lcm(a, b):
return abs(a*b) // math.gcd(a, b)
``````

Or, if you’re using NumPy, it’s come with an `lcm` function for quite some time now.

### In Python 3.9+

This is available as `math.lcm()`. It also takes any number of arguments, allowing you to find the lowest common multiple of more than 2 integers.

For example:

``````>>> from math import lcm
>>> lcm(2, 5, 7)
70
``````

``````def lcm(x, y):
from fractions import gcd # or can import gcd from `math` in Python 3
return x * y // gcd(x, y)
``````

To simplify your code a little:

``````def lcm(x, y):
for currentPossibleLCM in range(max(x,y), (x*y)+1)
if((currentPossibleLCM % x == 0) and (currentPossibleLCM % y == 0)):
return currentPossibleLCM
``````

Runtime: O(x*y)

This is not only for two numbers specifically but for finding LCM of an array of integers. (without using math.lcm())

``````import math
from functools import reduce

def lcm(arr):

l=reduce(lambda x,y:(x*y)//math.gcd(x,y),arr)
return l
``````