Does the order of functions in a Python script matter?

Question

Let\'s say I have two functions in my script: sum_numbers and print_sum. Their implementation is like this:

def sum_numbers(a, b):
             


        

Answer 1

It doesn't matter in which order the functions are created. It only matters when the call to the function is done:

def print_sum(a, b):
    print(sum_numbers(a, b))

def sum_numbers(a, b):
    return a + b

print_sum(1, 3)
# 4

that works because at the time print_sum is called both functions do exist. However if you call the function before defining sum_numbers it would fail because sum_numbers isn't defined yet:

def print_sum(a, b):
    print(sum_numbers(a, b))

print_sum(1, 3)

def sum_numbers(a, b):
    return a + b

throws:

---------------------------------------------------------------------------
NameError                                 Traceback (most recent call last)
 in ()
      2     print(sum_numbers(a, b))
      3 
----> 4 print_sum(1, 3)
      5 
      6 def sum_numbers(a, b):

 in print_sum(a, b)
      1 def print_sum(a, b):
----> 2     print(sum_numbers(a, b))
      3 
      4 print_sum(1, 3)
      5 

NameError: name 'sum_numbers' is not defined