Create app.py

app.py

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+# app.py
+# pip install gradio
+
+import gradio as gr
+
+# ----- Data -----
+inventory = [
+    (101, "Hammer", 120),
+    (102, "Screwdriver Set", 350),
+    (103, "Drill Machine", 2500),
+    (104, "Pliers", 180),
+    (105, "Wrench", 220),
+]
+
+INV = {pid: {"name": name, "price": price} for pid, name, price in inventory}
+
+
+# ----- Helpers -----
+def format_cart(cart):
+    if not cart:
+        return "Cart is empty."
+    lines = ["#  Item (ID) - Price"]
+    for i, item in enumerate(cart, start=1):
+        lines.append(f"{i}. {item['name']} ({item['id']}) - ${item['price']}")
+    return "\n".join(lines)
+
+def cart_dropdown_choices(cart):
+    # Each cart entry is removable individually (even duplicates)
+    choices = []
+    for idx, item in enumerate(cart):
+        label = f"{idx+1}: {item['name']} (ID {item['id']}) - ${item['price']}"
+        choices.append((label, idx))  # (display_label, value=index)
+    return choices
+
+
+# ----- Actions -----
+def add_to_cart(selected_id, cart):
+    if cart is None:
+        cart = []
+
+    if selected_id is None:
+        return (
+            gr.update(choices=cart_dropdown_choices(cart), value=None),
+            format_cart(cart),
+            "Please select a Product ID to add.",
+            "",
+            "",
+            cart,
+        )
+
+    item = INV.get(int(selected_id))
+    if not item:
+        return (
+            gr.update(choices=cart_dropdown_choices(cart), value=None),
+            format_cart(cart),
+            f"Product ID {selected_id} not found in inventory.",
+            "",
+            "",
+            cart,
+        )
+
+    cart.append({"id": int(selected_id), "name": item["name"], "price": item["price"]})
+
+    return (
+        gr.update(choices=cart_dropdown_choices(cart), value=None),
+        format_cart(cart),
+        f"Added: {item['name']} (ID {selected_id}) - ${item['price']}",
+        "",
+        "",
+        cart,
+    )
+
+def remove_from_cart(selected_cart_index, cart):
+    if cart is None:
+        cart = []
+
+    if not cart:
+        return (
+            gr.update(choices=[], value=None),
+            format_cart(cart),
+            "",
+            "Cart is empty — nothing to remove.",
+            "",
+            cart,
+        )
+
+    if selected_cart_index is None:
+        return (
+            gr.update(choices=cart_dropdown_choices(cart), value=None),
+            format_cart(cart),
+            "",
+            "Please select an item from the cart to remove.",
+            "",
+            cart,
+        )
+
+    idx = int(selected_cart_index)
+    if idx < 0 or idx >= len(cart):
+        return (
+            gr.update(choices=cart_dropdown_choices(cart), value=None),
+            format_cart(cart),
+            "",
+            "Invalid selection. Try again.",
+            "",
+            cart,
+        )
+
+    removed = cart.pop(idx)
+
+    return (
+        gr.update(choices=cart_dropdown_choices(cart), value=None),
+        format_cart(cart),
+        "",
+        f"Removed: {removed['name']} (ID {removed['id']}) - ${removed['price']}",
+        "",
+        cart,
+    )
+
+def calculate_total(cart):
+    if cart is None:
+        cart = []
+    total = sum(item["price"] for item in cart)
+    return f"${total}"
+
+
+# ----- UI -----
+product_choices = [(f"{pid}: {name} - ${price}", pid) for pid, name, price in inventory]
+
+with gr.Blocks(title="Hardware Store Billing") as demo:
+    gr.Markdown("## Hardware Store Billing (Add / Remove / Total)")
+
+    cart_state = gr.State([])
+
+    with gr.Row():
+        add_dropdown = gr.Dropdown(
+            label="Enter Product ID to Add to Cart",
+            choices=product_choices,
+            value=None,
+        )
+        remove_dropdown = gr.Dropdown(
+            label="Enter Index to Remove from Cart",
+            choices=[],
+            value=None,
+        )
+
+    with gr.Row():
+        add_btn = gr.Button("Add to Cart")
+        remove_btn = gr.Button("Remove from Cart")
+
+    cart_box = gr.Markdown("Cart is empty.", label="Your Cart")
+
+    add_msg = gr.Textbox(label="Add Item Message", interactive=False)
+    remove_msg = gr.Textbox(label="Remove Item Message", interactive=False)
+
+    with gr.Row():
+        total_btn = gr.Button("Calculate Total")
+        total_out = gr.Textbox(label="Total Cost", interactive=False)
+
+    # Wire actions
+    add_btn.click(
+        fn=add_to_cart,
+        inputs=[add_dropdown, cart_state],
+        outputs=[remove_dropdown, cart_box, add_msg, remove_msg, total_out, cart_state],
+    )
+
+    remove_btn.click(
+        fn=remove_from_cart,
+        inputs=[remove_dropdown, cart_state],
+        outputs=[remove_dropdown, cart_box, add_msg, remove_msg, total_out, cart_state],
+    )
+
+    total_btn.click(
+        fn=calculate_total,
+        inputs=[cart_state],
+        outputs=[total_out],
+    )
+
+demo.launch()