app.py

import gradio as gr

c_css = """
.ctt textarea { text-transform: lowercase; !important }
"""

def greet(name):
    return "Hello "+name

with gr.Blocks(css=c_css) as iface:
    inp=gr.Textbox(elem_classes="ctt")
    out=gr.Textbox()
    btn=gr.Button("push")
    btn.click(greet, inp, out)

iface.launch()