decorator for recursive functions

Question

i would like to implement decorator for recursive function, namely fibonnaciy numbers, idea is that as you know recursive function for large input takes too much time,for this example i have tried fibonacci numbers, but it returns following error : TypeError: unsupported operand type(s) for +: 'NoneType' and 'NoneType'

if i run code without decorator, it works fine and returns corresponding output, but with decorator it raises error, i would post code as well

           import time
            # start =time.time()
            def time_calculator(func):
                def n_th_number(n):
                    start = time.time()
            
                    print(func(n))
                    end = time.time()
                    print(f'fibonacci lasts for {end - start} second')
                return n_th_number
            @time_calculator
            def fibonacci(n):
                if n==0 or n==1:
                    return n
                else:
            
                   return fibonacci(n-1)+fibonacci(n-2)
            fibonacci(30)

please help me to understand what is wrong with my code?

full error :

1
fibonacci lasts for 0.0 second
0
fibonacci lasts for 0.0 second
Traceback (most recent call last):
  File "C:\Users\User\PycharmProjects\New_AI_Era\time_estimation.py", line 16, in <module>
    fibonacci(30)
  File "C:\Users\User\PycharmProjects\New_AI_Era\time_estimation.py", line 7, in n_th_number
    print(func(n))
          ^^^^^^^
  File "C:\Users\User\PycharmProjects\New_AI_Era\time_estimation.py", line 15, in fibonacci
    return fibonacci(n-1)+fibonacci(n-2)
           ^^^^^^^^^^^^^^
  File "C:\Users\User\PycharmProjects\New_AI_Era\time_estimation.py", line 7, in n_th_number
    print(func(n))
          ^^^^^^^
  File "C:\Users\User\PycharmProjects\New_AI_Era\time_estimation.py", line 15, in fibonacci
    return fibonacci(n-1)+fibonacci(n-2)
           ^^^^^^^^^^^^^^
  File "C:\Users\User\PycharmProjects\New_AI_Era\time_estimation.py", line 7, in n_th_number
    print(func(n))
          ^^^^^^^
  File "C:\Users\User\PycharmProjects\New_AI_Era\time_estimation.py", line 15, in fibonacci
    return fibonacci(n-1)+fibonacci(n-2)
           ^^^^^^^^^^^^^^
  File "C:\Users\User\PycharmProjects\New_AI_Era\time_estimation.py", line 7, in n_th_number
    print(func(n))
          ^^^^^^^
  File "C:\Users\User\PycharmProjects\New_AI_Era\time_estimation.py", line 15, in fibonacci
    return fibonacci(n-1)+fibonacci(n-2)
           ^^^^^^^^^^^^^^
  File "C:\Users\User\PycharmProjects\New_AI_Era\time_estimation.py", line 7, in n_th_number
    print(func(n))
          ^^^^^^^
  File "C:\Users\User\PycharmProjects\New_AI_Era\time_estimation.py", line 15, in fibonacci
    return fibonacci(n-1)+fibonacci(n-2)
           ^^^^^^^^^^^^^^
  File "C:\Users\User\PycharmProjects\New_AI_Era\time_estimation.py", line 7, in n_th_number
    print(func(n))
          ^^^^^^^
  File "C:\Users\User\PycharmProjects\New_AI_Era\time_estimation.py", line 15, in fibonacci
    return fibonacci(n-1)+fibonacci(n-2)
           ^^^^^^^^^^^^^^
  File "C:\Users\User\PycharmProjects\New_AI_Era\time_estimation.py", line 7, in n_th_number
    print(func(n))
          ^^^^^^^
  File "C:\Users\User\PycharmProjects\New_AI_Era\time_estimation.py", line 15, in fibonacci
    return fibonacci(n-1)+fibonacci(n-2)
           ^^^^^^^^^^^^^^
  File "C:\Users\User\PycharmProjects\New_AI_Era\time_estimation.py", line 7, in n_th_number
    print(func(n))
          ^^^^^^^
  File "C:\Users\User\PycharmProjects\New_AI_Era\time_estimation.py", line 15, in fibonacci
    return fibonacci(n-1)+fibonacci(n-2)
           ^^^^^^^^^^^^^^
  File "C:\Users\User\PycharmProjects\New_AI_Era\time_estimation.py", line 7, in n_th_number
    print(func(n))
          ^^^^^^^
  File "C:\Users\User\PycharmProjects\New_AI_Era\time_estimation.py", line 15, in fibonacci
    return fibonacci(n-1)+fibonacci(n-2)
           ^^^^^^^^^^^^^^
  File "C:\Users\User\PycharmProjects\New_AI_Era\time_estimation.py", line 7, in n_th_number
    print(func(n))
          ^^^^^^^
  File "C:\Users\User\PycharmProjects\New_AI_Era\time_estimation.py", line 15, in fibonacci
    return fibonacci(n-1)+fibonacci(n-2)
           ^^^^^^^^^^^^^^
  File "C:\Users\User\PycharmProjects\New_AI_Era\time_estimation.py", line 7, in n_th_number
    print(func(n))
          ^^^^^^^
  File "C:\Users\User\PycharmProjects\New_AI_Era\time_estimation.py", line 15, in fibonacci
    return fibonacci(n-1)+fibonacci(n-2)
           ^^^^^^^^^^^^^^
  File "C:\Users\User\PycharmProjects\New_AI_Era\time_estimation.py", line 7, in n_th_number
    print(func(n))
          ^^^^^^^
  File "C:\Users\User\PycharmProjects\New_AI_Era\time_estimation.py", line 15, in fibonacci
    return fibonacci(n-1)+fibonacci(n-2)
           ^^^^^^^^^^^^^^
  File "C:\Users\User\PycharmProjects\New_AI_Era\time_estimation.py", line 7, in n_th_number
    print(func(n))
          ^^^^^^^
  File "C:\Users\User\PycharmProjects\New_AI_Era\time_estimation.py", line 15, in fibonacci
    return fibonacci(n-1)+fibonacci(n-2)
           ^^^^^^^^^^^^^^
  File "C:\Users\User\PycharmProjects\New_AI_Era\time_estimation.py", line 7, in n_th_number
    print(func(n))
          ^^^^^^^
  File "C:\Users\User\PycharmProjects\New_AI_Era\time_estimation.py", line 15, in fibonacci
    return fibonacci(n-1)+fibonacci(n-2)
           ^^^^^^^^^^^^^^
  File "C:\Users\User\PycharmProjects\New_AI_Era\time_estimation.py", line 7, in n_th_number
    print(func(n))
          ^^^^^^^
  File "C:\Users\User\PycharmProjects\New_AI_Era\time_estimation.py", line 15, in fibonacci
    return fibonacci(n-1)+fibonacci(n-2)
           ^^^^^^^^^^^^^^
  File "C:\Users\User\PycharmProjects\New_AI_Era\time_estimation.py", line 7, in n_th_number
    print(func(n))
          ^^^^^^^
  File "C:\Users\User\PycharmProjects\New_AI_Era\time_estimation.py", line 15, in fibonacci
    return fibonacci(n-1)+fibonacci(n-2)
           ^^^^^^^^^^^^^^
  File "C:\Users\User\PycharmProjects\New_AI_Era\time_estimation.py", line 7, in n_th_number
    print(func(n))
          ^^^^^^^
  File "C:\Users\User\PycharmProjects\New_AI_Era\time_estimation.py", line 15, in fibonacci
    return fibonacci(n-1)+fibonacci(n-2)
           ^^^^^^^^^^^^^^
  File "C:\Users\User\PycharmProjects\New_AI_Era\time_estimation.py", line 7, in n_th_number
    print(func(n))
          ^^^^^^^
  File "C:\Users\User\PycharmProjects\New_AI_Era\time_estimation.py", line 15, in fibonacci
    return fibonacci(n-1)+fibonacci(n-2)
           ^^^^^^^^^^^^^^
  File "C:\Users\User\PycharmProjects\New_AI_Era\time_estimation.py", line 7, in n_th_number
    print(func(n))
          ^^^^^^^
  File "C:\Users\User\PycharmProjects\New_AI_Era\time_estimation.py", line 15, in fibonacci
    return fibonacci(n-1)+fibonacci(n-2)
           ^^^^^^^^^^^^^^
  File "C:\Users\User\PycharmProjects\New_AI_Era\time_estimation.py", line 7, in n_th_number
    print(func(n))
          ^^^^^^^
  File "C:\Users\User\PycharmProjects\New_AI_Era\time_estimation.py", line 15, in fibonacci
    return fibonacci(n-1)+fibonacci(n-2)
           ^^^^^^^^^^^^^^
  File "C:\Users\User\PycharmProjects\New_AI_Era\time_estimation.py", line 7, in n_th_number
    print(func(n))
          ^^^^^^^
  File "C:\Users\User\PycharmProjects\New_AI_Era\time_estimation.py", line 15, in fibonacci
    return fibonacci(n-1)+fibonacci(n-2)
           ^^^^^^^^^^^^^^
  File "C:\Users\User\PycharmProjects\New_AI_Era\time_estimation.py", line 7, in n_th_number
    print(func(n))
          ^^^^^^^
  File "C:\Users\User\PycharmProjects\New_AI_Era\time_estimation.py", line 15, in fibonacci
    return fibonacci(n-1)+fibonacci(n-2)
           ^^^^^^^^^^^^^^
  File "C:\Users\User\PycharmProjects\New_AI_Era\time_estimation.py", line 7, in n_th_number
    print(func(n))
          ^^^^^^^
  File "C:\Users\User\PycharmProjects\New_AI_Era\time_estimation.py", line 15, in fibonacci
    return fibonacci(n-1)+fibonacci(n-2)
           ^^^^^^^^^^^^^^
  File "C:\Users\User\PycharmProjects\New_AI_Era\time_estimation.py", line 7, in n_th_number
    print(func(n))
          ^^^^^^^
  File "C:\Users\User\PycharmProjects\New_AI_Era\time_estimation.py", line 15, in fibonacci
    return fibonacci(n-1)+fibonacci(n-2)
           ^^^^^^^^^^^^^^
  File "C:\Users\User\PycharmProjects\New_AI_Era\time_estimation.py", line 7, in n_th_number
    print(func(n))
          ^^^^^^^
  File "C:\Users\User\PycharmProjects\New_AI_Era\time_estimation.py", line 15, in fibonacci
    return fibonacci(n-1)+fibonacci(n-2)
           ^^^^^^^^^^^^^^
  File "C:\Users\User\PycharmProjects\New_AI_Era\time_estimation.py", line 7, in n_th_number
    print(func(n))
          ^^^^^^^
  File "C:\Users\User\PycharmProjects\New_AI_Era\time_estimation.py", line 15, in fibonacci
    return fibonacci(n-1)+fibonacci(n-2)
           ^^^^^^^^^^^^^^
  File "C:\Users\User\PycharmProjects\New_AI_Era\time_estimation.py", line 7, in n_th_number
    print(func(n))
          ^^^^^^^
  File "C:\Users\User\PycharmProjects\New_AI_Era\time_estimation.py", line 15, in fibonacci
    return fibonacci(n-1)+fibonacci(n-2)
           ^^^^^^^^^^^^^^
  File "C:\Users\User\PycharmProjects\New_AI_Era\time_estimation.py", line 7, in n_th_number
    print(func(n))
          ^^^^^^^
  File "C:\Users\User\PycharmProjects\New_AI_Era\time_estimation.py", line 15, in fibonacci
    return fibonacci(n-1)+fibonacci(n-2)
           ^^^^^^^^^^^^^^
  File "C:\Users\User\PycharmProjects\New_AI_Era\time_estimation.py", line 7, in n_th_number
    print(func(n))
          ^^^^^^^
  File "C:\Users\User\PycharmProjects\New_AI_Era\time_estimation.py", line 15, in fibonacci
    return fibonacci(n-1)+fibonacci(n-2)
           ~~~~~~~~~~~~~~^~~~~~~~~~~~~~~
TypeError: unsupported operand type(s) for +: 'NoneType' and 'NoneType'

Answer 1

The wrapper still needs to call the function and return the value that it would have returned.

           import time
            # start =time.time()
            def time_calculator(func):
                def n_th_number(n):
                    start = time.time()
                    result = func(n)
                    print(result)
                    end = time.time()
                    print(f'fibonacci lasts for {end - start} second')
                    return result
                return n_th_number