Expand component to fill remaining space?

I have some divs, buttons, and dropdowns which I would like to fill the remaining space available to them? How can I do such a thing?

An example is:

import dash
import dash_bootstrap_components as dbc

app = dash.Dash(external_stylesheets=[dbc.themes.CERULEAN])

app.layout = \
    dbc.Container \
                    dbc.Row([dbc.Button("Graph here", style={"width": "100%"})]), # make this fill the available height
                    dbc.Row([dbc.Button("Load file",  style={"width": "50%"}), dbc.Button("Load a different file") # make this button fill available width]),
                ], width=9),
                    dbc.Row([dbc.Button("Choose data",  style={"width": "100%"})]),
                    dbc.Row([dbc.Button("Change graph", style={"width": "100%"})]), # make this fill available height
                ], width=3)
        ], fluid=True)

if __name__ == "__main__":
    app.run_server(debug=False, port=8050)