a = 8, b = 27
Write the code to find the greatest common divisor of two numbers.
Below you'll find the Python code to find the greatest common divisor (GCD) for two given numbers using the Euclidean algorithm:

```python
def gcd(a, b):
    while b:
        a, b = b, a % b
    return a

# Test the function
a = 8 
b = 27
print(f'The Greatest Common Divisor of {a} and {b} is {gcd(a, b)}') 
```

The above code calculates the GCD by the iterative method of subtraction.