My goal:

1. drop a list of files.
2. Read files and extract columns.
3. Dynamically generate dropdown componenets so the user can select the source and target columns.
4. I need to return (globally) all the selections, so I can use them with process_files() function. I think (3) it should be solved using gr.State([]) but I am not sure how to update it. here is my code:

Function to process files

import gradio as gr
import pandas as pd


def process_files(files, selections):
    results = []

    for file, selection in zip(files, selections):
        file_name = file.name
        source_col, target_col, source_lang, target_lang = selection
        try:
            if file_name.endswith(".csv"):
                df = pd.read_csv(file.name)
            elif file_name.endswith(".xlsx"):
                df = pd.read_excel(file.name, engine="openpyxl")
            else:
                continue  # Skip unsupported files

            # Extract selected columns
            extracted_data = df[[source_col, target_col]]

            results.append(
                f"✅ Processed {file_name} ({source_lang} → {target_lang})")
        except Exception as e:
            results.append(f"Error processing {file_name}: {str(e)}")

    return "\n".join(results)

Gradio Interface

with gr.Blocks() as demo:
    gr.Markdown("## Upload Multiple Files and Select Columns")

    file_input = gr.File(file_types=[
                         ".csv", ".xlsx"], label="Drop your files here", interactive=True, file_count="multiple")

    all_selections = gr.State([])

    @gr.render(inputs=[file_input], triggers=[file_input.change])
    def generate_column_selectors(files):
        if not files:
            return "## No Files Uploaded", []  # Reset selections

        with gr.Column():
            for file in files:
                try:
                    if file.name.endswith(".csv"):
                        df = pd.read_csv(file.name)
                    elif file.name.endswith(".xlsx"):
                        df = pd.read_excel(file.name, engine="openpyxl")
                    else:
                        continue 

                    with gr.Row():
                        gr.Markdown(f"**{file.name}**")  # Display filename
                        source_col = gr.Dropdown(
                            df.columns.tolist(), label="Source Column", interactive=True)
                        target_col = gr.Dropdown(
                            df.columns.tolist(), label="Target Column", interactive=True)
                        source_lang = gr.Textbox(
                            label="Source Language", placeholder="e.g., English", interactive=True)
                        target_lang = gr.Textbox(
                            label="Target Language", placeholder="e.g., French", interactive=True)

                    all_selections.append(
                        (source_col, target_col, source_lang, target_lang)) # this does not work.

                except Exception as e:
                    gr.Markdown(f"Error processing {file.name}: {str(e)}")
    submit_button = gr.Button("Submit & Process", interactive=True)
    output_text = gr.Markdown()

    submit_button.click(process_files, inputs=[
                        file_input, all_selections], outputs=[output_text])

demo.launch()