Python supports the definition of the functions which is a good way to define a piece of code that is executed at multiple places in the program. A function is defined using the keyword def.

Input:

source_code/appendix_c_python/example13_function.py
def rectangle_perimeter(a, b):
        return 2 * (a + b)

print 'Let a rectangle have its sides 2 and 3 units long.'
print 'Then its perimeter is', rectangle_perimeter(2, 3), 'units.'
print 'Let a rectangle have its sides 4 and 5 units long.'
print 'Then its perimeter is', rectangle_perimeter(4, 5), 'units.'

Output:

$ python example13_function.py 
Let a rectangle have its sides 2 and 3 units long.
Then its perimeter is 10 units.
Let a rectangle have its sides 4 and 5 units long.
Then its perimeter is 18 units.