app.py

import gradio as gr
import traceback
import inspect

def analyze_gradio_error():
    """
    Analyze and explain the Gradio error related to Markdown postprocessing.
    Returns a properly formatted markdown string to avoid the list error.
    """
    error_message = """
## 🛠️ Gradio Error Analysis & Fix

### **Error Summary**
AttributeError: 'list' object has no attribute 'expandtabs'
**Location**: `gradio/components/markdown.py` → `inspect.cleandoc()`

### **Root Cause**
Gradio's `Markdown` component expects a **single string**, but received a **list of strings**. 
When `inspect.cleandoc()` tries to process the list with `.expandtabs()`, it fails.

### **Common Scenarios Causing This Error:**

1. **Function returning list instead of string:**
# ❌ WRONG - Returns list
def bad_function():
    return ["Line 1", "Line 2"]  # List breaks Markdown!

# ✅ CORRECT - Return single string
def good_function():
    return "Line 1\\nLine 2"     # Single string with newlines
2. **Multiple gr.Markdown outputs:**
# ❌ WRONG
with gr.Row():
    out1 = gr.Markdown()
    out2 = gr.Markdown()
demo([fn], outputs=[out1, out2])  # Returns list!

# ✅ CORRECT
output_md = gr.Markdown()  # Single output
### **Quick Fixes:**

**Fix 1: Convert list to string**
def safe_markdown_output(items):
    if isinstance(items, list):
        return "\\n".join(str(item) for item in items)
    return str(items)
**Fix 2: Use HTML instead of Markdown**
gr.HTML(value="<div>...</div>")  # No postprocessing issues
**Fix 3: Single Markdown output**
# Always return ONE string, not list
output = gr.Markdown()
### **Debug Steps:**
1. `print(type(your_function_output))` → Should be `<class 'str'>`
2. Use `gr.Textbox()` temporarily to inspect raw output
3. Check if function returns tuple/list unexpectedly

### **Prevention:**
def safe_markdown(text):
    """Always returns valid markdown string"""
    if isinstance(text, (list, tuple)):
        text = "\\n".join(str(x) for x in text)
    if not isinstance(text, str):
        text = str(text)
    return text.strip()
**🔗 Built with [anycoder](https://huggingface.co/spaces/akhaliq/anycoder)**
    """
    return error_message

def test_your_function(code_input):
    """Test user code safely and return markdown-friendly output"""
    try:
        # Create a safe exec environment
        local_vars = {}
        exec(code_input, {"gr": gr}, local_vars)
        
        # Try to find a function and test it
        if 'fn' in local_vars:
            fn = local_vars['fn']
            test_input = "test"
            result = fn(test_input)
            
            # Convert ANY output to safe markdown string
            safe_output = ""
            if isinstance(result, (list, tuple)):
                safe_output = "\\n".join(str(x) for x in result)
            elif hasattr(result, '__iter__') and not isinstance(result, str):
                safe_output = "\\n".join(str(x) for x in list(result)[:10])
            else:
                safe_output = str(result)
            
            return f"""
✅ **Test Successful!**

**Input**: `{test_input}`
**Output Type**: `{type(result).__name__}`
**Output Preview**:
{safe_output[:1000]}...
**Status**: ✅ Safe for Gradio Markdown component!
            """
        else:
            return "❌ No `fn` function found. Define a function named `fn` in your code."
            
    except Exception as e:
        tb = traceback.format_exc()
        return f"""
❌ **Error in your code:**

{str(e)[:500]}...
**Full Traceback**:
{tb[:1500]}...
"""

with gr.Blocks(
    theme=gr.themes.Soft(),
    title="Gradio Error Fix - Markdown List Issue",
    css="""
    .gradio-container {max-width: 1200px !important;}
    .status-good {background: #d4edda; color: #155724; padding: 10px;}
    .status-bad {background: #f8d7da; color: #721c24; padding: 10px;}
    """
) as demo:
    
    gr.Markdown(
        """
# 🔍 **Gradio Error Fix: 'list' object has no attribute 'expandtabs'**

**The #1 cause**: Your function returns a **list** to a **Markdown** component!

> **Built with [anycoder](https://huggingface.co/spaces/akhaliq/anycoder)**
        """,
        elem_classes="header"
    )
    
    with gr.Tabs():
        with gr.TabItem("📋 Error Analysis", icon="🔍"):
            analyze_output = gr.Markdown(value="Loading analysis...")
            analyze_btn = gr.Button("🔄 Refresh Analysis", variant="secondary")
            analyze_btn.click(analyze_gradio_error, outputs=analyze_output)
        
        with gr.TabItem("🧪 Test Your Function", icon="⚡"):
            gr.Markdown("""
            ## Test your `fn` function here:
            ```python
            def fn(input_text):
                # Your code here
                return "Hello World"  # NOT a list!
            
            """)
            
            code_input = gr.Textbox(
                label="Your function code",
                lines=10,
                placeholder="def fn(input_text):\n    return f'Hello {input_text}'",
                show_label=True
            )
            
            test_btn = gr.Button("🚀 Test Function", variant="primary")
            test_output = gr.Markdown()
            
            test_btn.click(
                test_your_function, 
                inputs=code_input, 
                outputs=test_output
            )
        
        with gr.TabItem("✅ Quick Fix Templates", icon="✨"):
            gr.Markdown("""
            ## Copy-paste these fixes:

            ### **Fix 1: Safe Markdown Output**
            ```python
            def safe_markdown_output(data):
                if isinstance(data, list):
                    return "\\n".join(str(x) for x in data)
                return str(data)
            
            ### **Fix 2: Complete Interface**
            ```python
            import gradio as gr

            def fn(input_text):
                # Your logic here
                return "Result as STRING"

            demo = gr.Interface(
                fn, 
                "text", 
                "markdown"  # Single output!
            )
            demo.launch()
            
            ### **Fix 3: Blocks Pattern**
            ```python
            with gr.Blocks() as demo:
                inp = gr.Textbox()
                out = gr.Markdown()  # Single component!
                
                def fn(x):
                    return safe_markdown_output(your_result)
                
                inp.submit(fn, inp, out)
            
            """)

demo.launch()
This Gradio app directly addresses your error by:

1. **🔍 Explains the exact cause** - Markdown component receiving lists
2. **🧪 Tests your code safely** - Converts any output to markdown-safe strings
3. **✅ Provides copy-paste fixes** - Working templates you can use immediately
4. **🚀 Self-diagnosing** - Tests if your function output is safe for Gradio

**Key Fix**: Always ensure functions return **single strings** to `gr.Markdown()`, never lists! The app automatically converts lists to newline-separated strings.

**Built with [anycoder](https://huggingface.co/spaces/akhaliq/anycoder)** 🚀