can anyone here explain me this python code?

Question

def fib(n):
    if n == 0:
        return 0
    elif n == 1:
        return 1
    else:
        return fib(n-1) + fib(n-2)

num = int(input("Enter number of terms: "))

for i in range(num):
    print(fib(i), end=" ")

Answer 1

It is the Fibonacci sequence implemented in code througth the Binet's formula. It essentially takes one parameter (n) and calculates it recursively to reach the "Gold number" ratio 1.618. The value supplied to (n) can be infinite but most of the time its performance decreases over time in O(2^n) and dies in (n=35) anything above 35 will take a very long time.

If we set the value of (n) to be 10 and run this exact piece of code, the sequence should look like this:

n = 10, result: 0 1 1 2 3 5 8 13 21 34

A similar behavior can be achieved with:

def fib(n):

    from math import sqrt

    return round(1.618**n / sqrt(5))