Add iterative Fibonacci implementation

maths/fibonacci_iterative.py

@@ -0,0 +1,33 @@
+def fibonacci_iterative(term_index: int) -> int:
+    """
+    Return the Fibonacci number at a given index using an iterative approach.
+
+    Parameters:
+        term_index (int): Index in the Fibonacci sequence.
+            Must be a non-negative integer.
+
+    Returns:
+        int: The Fibonacci number at the specified index.
+
+    Examples:
+    >>> fibonacci_iterative(0)
+    0
+    >>> fibonacci_iterative(1)
+    1
+    >>> fibonacci_iterative(7)
+    13
+    """
+    if term_index < 0:
+        raise ValueError("term_index must be a non-negative integer.")
+
+    if term_index <= 1:
+        return term_index
+
+    prev, curr = 0, 1
+    for _ in range(2, term_index + 1):
+        prev, curr = curr, prev + curr
+    return curr
+
+
+if __name__ == "__main__":
+    print(fibonacci_iterative(7))  # expected 13