Fix input validation, typing, and documentation in Fibonacci DP example

Author: Sangeeth62880

dynamic_programming/fibonacci.py

@@ -1,50 +1,63 @@
 """
-This is a pure Python implementation of Dynamic Programming solution to the fibonacci
-sequence problem.
+This is a pure Python implementation of a dynamic programming solution
+to generate the Fibonacci sequence.
 """
 
+from typing import List
+
 
 class Fibonacci:
     def __init__(self) -> None:
-        self.sequence = [0, 1]
+        self.sequence: List[int] = [0, 1]
 
-    def get(self, index: int) -> list:
+    def get(self, index: int) -> List[int]:
         """
-        Get the Fibonacci number of `index`. If the number does not exist,
-        calculate all missing numbers leading up to the number of `index`.
+        Return the Fibonacci sequence up to the given index (exclusive).
+
+        Args:
+            index: The number of Fibonacci values to generate.
+
+        Returns:
+            A list of Fibonacci numbers up to the given index.
+
+        Raises:
+            ValueError: If index is a negative integer.
 
         >>> Fibonacci().get(10)
         [0, 1, 1, 2, 3, 5, 8, 13, 21, 34]
         >>> Fibonacci().get(5)
         [0, 1, 1, 2, 3]
         """
+        if index < 0:
+            raise ValueError("index must be a non-negative integer")
+
         if (difference := index - (len(self.sequence) - 2)) >= 1:
             for _ in range(difference):
                 self.sequence.append(self.sequence[-1] + self.sequence[-2])
+
         return self.sequence[:index]
 
 
 def main() -> None:
     print(
-        "Fibonacci Series Using Dynamic Programming\n",
-        "Enter the index of the Fibonacci number you want to calculate ",
-        "in the prompt below. (To exit enter exit or Ctrl-C)\n",
-        sep="",
+        "Fibonacci Series Using Dynamic Programming\n"
+        "Enter the number of Fibonacci values to generate.\n"
+        "(Type 'exit' or press Ctrl-C to quit)\n"
     )
+
     fibonacci = Fibonacci()
 
     while True:
         prompt: str = input(">> ")
-        if prompt in {"exit", "quit"}:
+
+        if prompt.lower() in {"exit", "quit"}:
             break
 
         try:
-            index: int = int(prompt)
-        except ValueError:
-            print("Enter a number or 'exit'")
-            continue
-
-        print(fibonacci.get(index))
+            index = int(prompt)
+            print(fibonacci.get(index))
+        except ValueError as exc:
+            print(f"Error: {exc}")
 
 
 if __name__ == "__main__":