Fibonacci 2 Ways | Python Fiddle

def recursive_fib(n):
    '''This function will recursively generate fibonacci numbers.
    It's very slow and intensive, and doesn't work well for large numbers.
    It re-generates every fibonacci number <= n for each layer = too much recursion
    '''
    try:
        assert n>0
        assert type(n) is int
        
        if (n==1 or n==2):
            return 1
        else:
            return recursive_fib(n-1) + recursive_fib(n-2)
    except AssertionError:
        return AssertionError
    
def generative_fib(n):
    '''Start at the beginning, and calculate the nth fibonacci numbers.
    Only calculates each fibonacci number once for each call
    '''
    try:
		assert n>0
        assert type(n) is int
        
        x = 1
        y=1
        
        for _ in xrange(n):
            x,y = y, x+y
        return x
    except AssertionError:
        return AssertionError
    
print generative_fib(5)
print recursive_fib(5) ##almost no difference in speed

print generative_fib(30)
print recursive_fib(30) ##any difference?

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