Create app.py

app.py

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+# app.py
+"""Simple Unit Converter (Gradio) for Hugging Face Spaces.
+- Put this file at the repo root as `app.py` (Spaces uses this as the entry point).
+- Minimal dependencies: gradio only.
+"""
+
+import gradio as gr
+
+# --- Unit factors to a base unit ---
+UNITS = {
+    "Mass": {
+        "kg": 1.0,
+        "g": 0.001,
+        "lb (pound)": 0.45359237,
+        "oz (ounce)": 0.028349523125
+    },
+    "Length": {
+        "m": 1.0,
+        "cm": 0.01,
+        "mm": 0.001,
+        "ft (foot)": 0.3048,
+        "in (inch)": 0.0254
+    },
+    "Volume": {
+        "L (liter)": 1.0,
+        "mL (milliliter)": 0.001,
+        "US gallon": 3.785411784,
+        "US quart": 0.946352946
+    },
+    # Temperature handled with formulas instead of factors
+    "Temperature": ["C", "F", "K"]
+}
+
+def update_units(category):
+    """Update From/To dropdowns when Category changes."""
+    if category == "Temperature":
+        choices = UNITS["Temperature"]
+    else:
+        choices = list(UNITS[category].keys())
+    from_default = choices[0]
+    to_default = choices[1] if len(choices) > 1 else choices[0]
+    return gr.update(choices=choices, value=from_default), gr.update(choices=choices, value=to_default)
+
+def convert(value, category, from_unit, to_unit, precision):
+    """Convert `value` from `from_unit` to `to_unit` inside `category`."""
+    # Input validation
+    try:
+        val = float(value)
+    except Exception:
+        return "❗ Enter a valid number."
+
+    # quick return if same unit
+    if from_unit == to_unit:
+        fmt = f"{{:.{precision}f}}"
+        return f"{fmt.format(val)} {from_unit} = {fmt.format(val)} {to_unit}"
+
+    # Temperature conversions (Celsius as intermediate)
+    if category == "Temperature":
+        # to Celsius
+        if from_unit == "C":
+            c = val
+        elif from_unit == "F":
+            c = (val - 32) * 5.0 / 9.0
+        elif from_unit == "K":
+            c = val - 273.15
+        else:
+            return "❗ Unknown temperature unit."
+
+        # from Celsius to target
+        if to_unit == "C":
+            res = c
+        elif to_unit == "F":
+            res = c * 9.0 / 5.0 + 32
+        elif to_unit == "K":
+            res = c + 273.15
+        else:
+            return "❗ Unknown temperature unit."
+    else:
+        # factor-based conversion: value -> base -> target
+        factors = UNITS[category]
+        try:
+            f_from = factors[from_unit]
+            f_to = factors[to_unit]
+        except KeyError:
+            return "❗ Unknown unit for selected category."
+        value_in_base = val * f_from
+        res = value_in_base / f_to
+
+    fmt = f"{{:.{precision}f}}"
+    return f"{fmt.format(val)} {from_unit} = {fmt.format(res)} {to_unit}"
+
+# --- Build Gradio UI ---
+with gr.Blocks() as demo:
+    gr.Markdown("## 🔁 Simple Unit Converter\nChoose category, units, value, then press Convert.")
+    with gr.Row():
+        category_dd = gr.Dropdown(choices=list(UNITS.keys()), value="Mass", label="Category")
+        precision = gr.Slider(minimum=0, maximum=6, step=1, value=4, label="Decimals")
+    with gr.Row():
+        from_dd = gr.Dropdown(choices=list(UNITS["Mass"].keys()), value="kg", label="From unit")
+        to_dd = gr.Dropdown(choices=list(UNITS["Mass"].keys()), value="g", label="To unit")
+    value_in = gr.Number(value=1.0, label="Value to convert")
+    convert_btn = gr.Button("Convert")
+    output_txt = gr.Textbox(label="Result", interactive=False)
+
+    # callbacks
+    category_dd.change(fn=update_units, inputs=category_dd, outputs=[from_dd, to_dd])
+    convert_btn.click(fn=convert, inputs=[value_in, category_dd, from_dd, to_dd, precision], outputs=output_txt)
+
+# Entry point for Spaces
+if __name__ == "__main__":
+    demo.launch()