finding Fibonacci numbers

LeetCode

Author: SanjarH

fib_numbers.py

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+# Learn Python together
+
+""" Write a function to calculate the Fibonacci numbers.
+- Fibonacci numbers commonly denoted F(n) form a sequence, 
+called the Fibonacci sequence, such that each number is the sum of
+the two preceding ones, starting from 0 and 1. That is,
+F(0) = 0, F(1) = 1
+F(n) = F(n - 1) + F(n - 2), for n > 1. """
+
+# Solution
+def fibonacci(n):    
+    if n <= 0:
+        return 0
+    elif n == 1:
+        return 1                     
+    return fibonacci(n-1) + fibonacci(n-2) # recursive case 
+           
+# Check    
+print(fibonacci(5)) # Output -> 5
+print(fibonacci(12)) # Output -> 144
+print(fibonacci(-11)) # Output -> 0