Fix calculator bugs and add calculation history feature

gradio_calculator.py

@@ -1,41 +1,101 @@
 import gradio as gr
 
 
-def calculate(num1, num2, operation):
+def format_number(x: float) -> str:
+    # FIX (Bug 3): format the result so users never see float noise
+    # such as 0.30000000000000004 for 0.1 + 0.2.
+    if x == int(x) and abs(x) < 1e15:
+        return str(int(x))
+    return f"{x:.10g}"
+
+
+def render_history(history: list) -> str:
+    # NEW FEATURE: render the history list as numbered Markdown lines.
+    if not history:
+        return "_No calculations yet._"
+    return "\n".join(f"{i + 1}. {entry}" for i, entry in enumerate(history))
+
+
+def calculate(num1, num2, operation, history):
+    history = history or []
+
+    # FIX (Bug 2): gr.Number returns None for empty fields, and float(None)
+    # raises TypeError (not ValueError), which crashed the app. Guard first.
+    if num1 is None or num2 is None:
+        return "Please enter both numbers", history, render_history(history)
+
     try:
-        num1 = float(num1)
-        num2 = float(num2)
-
-        if operation == "+":
-            result = num1 + num2
-        elif operation == "-":
-            result = num1 - num2
-        elif operation == "*":
-            result = num1 * num2
-        elif operation == "/":
-            if num2 == 0:
-                return "Cannot divide by zero"
-            result = num1 / num2
-        else:
-            return "Invalid operation"
-
-        return result
-    except ValueError:
-        return "Please enter valid numbers"
-
-
-with gr.Blocks() as demo:
+        a = float(num1)
+        b = float(num2)
+    except (ValueError, TypeError):
+        return "Please enter valid numbers", history, render_history(history)
+
+    if operation == "+":
+        result = a + b
+    elif operation == "-":
+        result = a - b
+    elif operation == "*":
+        result = a * b
+    elif operation == "/":
+        if b == 0:
+            return "Cannot divide by zero", history, render_history(history)
+        result = a / b
+    else:
+        return "Invalid operation", history, render_history(history)
+
+    result_text = format_number(result)
+
+    # NEW FEATURE: append this successful calculation to the history and
+    # return the updated list plus its rendered form.
+    entry = f"{format_number(a)} {operation} {format_number(b)} = {result_text}"
+    history = history + [entry]
+
+    return result_text, history, render_history(history)
+
+
+def clear_history():
+    # NEW FEATURE: reset history to empty when Clear History is clicked.
+    return [], "_No calculations yet._"
+
+
+with gr.Blocks(title="Simple Calculator") as demo:
     gr.Markdown("# Simple Calculator")
 
+    # NEW FEATURE: per-session storage for the calculation history.
+    history_state = gr.State([])
+
     with gr.Row():
         num1 = gr.Number(label="First number")
         operation = gr.Dropdown(["+", "-", "*", "/"], label="Operation", value="+")
         num2 = gr.Number(label="Second number")
 
-    calc_button = gr.Button("Calculate")
-    output = gr.Textbox(label="Result")
+    with gr.Row():
+        calc_button = gr.Button("Calculate", variant="primary")
+        # NEW FEATURE: button to clear the history.
+        clear_button = gr.Button("Clear History")
+
+    output = gr.Textbox(label="Result", interactive=False)
+
+    # NEW FEATURE: collapsible panel showing past calculations.
+    with gr.Accordion("History", open=True):
+        history_display = gr.Markdown("_No calculations yet._")
+
+    # FIX (Bug 1): inputs must be in the order calculate() expects
+    # (num1, num2, operation). The original passed them swapped, so every
+    # calculation failed with "Please enter valid numbers".
+    calc_button.click(
+        fn=calculate,
+        inputs=[num1, num2, operation, history_state],
+        outputs=[output, history_state, history_display],
+    )
 
-    calc_button.click(fn=calculate, inputs=[num1, num2, operation], outputs=output)
+    # NEW FEATURE: wire the Clear History button.
+    clear_button.click(
+        fn=clear_history,
+        inputs=None,
+        outputs=[history_state, history_display],
+    )
 
 
-demo.launch()
+if __name__ == "__main__":
+    demo.launch()