Can I use python3 classes inside a Flask app?
Flask is "just" a framework. It is still executed and managed by the "normal" Python interpreter so the question "how Flask would handle these instances" is nonexistent.
Define classes and use their instances as you would in any other Python project/snippet, however it might be beneficial to think where to define them.
It will not make sense inside a route since the class will be redefined every time a request is received, but the how is exactly the same.
I'm designing a Flask app that graphs some weather data for several cities. It makes sense to me to use a "City" class that handles the fetching and parsing of the data every time the page is loaded. However, what I'm not sure about is how Flask would handle these instances. Is Flask "smart" enough to know to release the memory for these instances after the page is served? Or will it just gradually consume more and more memory?
Alternatively, would I just be able to create a single global class instance for each city OUTSIDE of the "@app.route" functions that I could use whenever a page is requested?
The deployment server will be Windows IIS using FastCGI, in case that matters at all.