Where to implement python classes in Django?
Distinct to similar frameworks, you can put your Python code anywhere in your project, provided you can reference them later by their import path (model classes are partially an exception, though):

Applications are referenced by their import path (or an AppConfig import path). Although there's some magic involving test.py and models.py, most of the times the import / reference is quite explicit.
Views are referenced by urls.py files, but imported as regular python import path.
Middlewares are referenced by strings which denote an import path ending with their class name.
Other settings you normally don't configure are also full import paths.

The exception to this explicitness is:

models.py, test.py, admin.py : They have special purposes and may not exist, providing:

You will not need any model in your app, and will provide an AppConfig (instead of just the app name) in your INSTALLED_APPS.
You will not rely on autodiscovery for admin classes in your app.
You don't want to make tests on your app, or will specify a non-default path for your app-specific test command run.

templates and static files: your project will rely on per-app loaders for your static files and for your templates files, and ultimately there's a brute-force search in each of your apps: their inner static/ and templates/ directories, if exist, are searched for those files.

Everything else is just normal python code and, if you need to import them from any view, you just do a normal import sentence for them (since view code is imported with the normal Python import mechanism).
I'm learning Django on my own and I can't seem to get a clue of where I implement a regular Python class. What I mean is, I don't know where do the Python classes I write go. Like they go in a separate file and then are imported to the views.py or are the classes implemented inside the views.py file?
Example I want to implement a Class Alphabet, should I do this in a separate file inside the module or just implement the functions inside the views.py file?