Providing Default Value for User Input

[N?ant Humain]

I have just begun learning Python so that I can write a simple script
to make modification of a file used by another Python script easier.
This file is basically a list of regular expressions. What I want to
do is allow the user to select one of these regular expressions to
modify, but I've realized I know of no way to provide a default value
for user input. I could choose to show the regular expression the user
has chosen and simply allow the user to retype it and modify it from
there, but that is time consuming and error prone. Does Python support
a way to do this? If worse comes to worst, is there a way I could
write such code on my own without having to write a C-based module
(I'd like to stick to Python code only since some users will be
running this script on Windows without a C compiler)?