What will be happening if we change the code of a flask application while the server is still running...?

Question

I am new to python and I have a flask api say "versionupgrade" .What it basically dose is it triggers a bash script which in return replaces the old code with the new code and restart the apache server.. so the api flow is like this:

app.route("/api/v1/versionupgrade", methods=['POST'])
...
...
<triggers the bash script>
<the code gets replaced>
..
..
<apache server is restarted>

What i like to know is how the flask application proceeds without any error even if the code is altered..

I know that the changes gets reflected only when the flask server is restarted

Dose he code is stored in any sort of memory while executing

Anyone care to explain

thanks :)