In this example, we will learn how to calculate the greatest common divisor(GCD) in Python.

### 2. Method

In order to get the greatest common divisor of *x* and *y*, we need to use the for loop for variable *d* from 1 to the minimum of *x* and *y*, and checking the remainders of *x* and *y* dividing *d*. If the remainders are zero, *d* will be recorded as the common divisor of *x* and *y*. When the loop ends, we can get the maximum of all recorded *d*, i.e. the greatest common divisor.

### Source Code

```
#!/usr/bin/env python3
# -*- coding: utf-8 -*-
# Define the function to find the greatest common divisor
def hcf(x, y):
# Get the minimum of two numbers
if x > y:
smaller = y
else:
smaller = x
# Using a for loop to checking the remainder
for i in range(1, smaller + 1):
if ((x % i == 0) and (y % i == 0)):
# If all are zero, then assign
hcf = i
return hcf
# Enter two numbers
num1 = int(input("Enter the first number: "))
num2 = int(input("Enter the second number: "))
print("The greatest common divisor: ", hcf(num1, num2))
```

```
Enter the first number: 4
Enter the second number: 8
The greatest common divisor: 4
Enter the first number: 24
Enter the second number: 45
The greatest common divisor: 3
```