Fibonacci_Number.py

from functools import lru_cache

print("\n---------- Fibonacci Number Calculator ----------\n")

while True:
    try:       
        # Number of terms                                                                              
        n = int(input("Enter nth term ()\n(Note: Term count starts at 0): "))      
        if n < 0:                                                   
            print("Input must be a positive integer!\n")            
        else:                                                       
            break                                                   
    except:                                                         
        print("Invalid input! Try again.\n")                        


@lru_cache(maxsize=None)    # Optimizes the recursion implementation

# Recursive function:
def f(n): 

    # Base case 1:
    if n == 1:
        return 0 # Returns the 1st term of the sequence if number of terms is 1

    # Base case 2:
    elif n == 2:
        return 1 # Returns the 2nd term of the sequence if number of terms is 2
    
    # Recursive case:
    elif n > 2:
        # Calculates & returns the next terms 
        # of the sequence using a recursive call:
        return f(n - 1) + f(n - 2) 

print("--------------------------------------------------")

# Output
print("f_", n, " = ", f(n), sep='')   

print("--------------------------------------------------\n")