app.py

def copy(src_sentence):
    return src_sentence
        
with gr.Blocks(title="Copier") as demo:
    gr.Markdown("# Copier")
    with gr.Row():
        with gr.Column():
            src_sentence = gr.Textbox(label="Source text", placeholder="Write your text...")
        with gr.Column():
            tgt_sentence = gr.Textbox(label="Copy", placeholder="Copy will show here...")
    btn = gr.Button("Copy!")
    btn.click(fn=copy, inputs=[src_sentence], outputs=[tgt_sentence])

demo.launch()