Pattern matching accepted for Python

Re:Pattern matching accepted for Python by amirkdv on Wednesday February 10, 2021 @12:00AM (#26085886)

This part is truly strange. This example from the tutorial drove it home for me:

    match event.get():
        case Click(position=(x, y)):
            handle_click_at(x, y)
        case KeyPress(key_name="Q") | Quit():
            game.quit()

where `Click(position=(x, y))` is not at all what one would expect.

What I still don't understand is: does the new syntax magically do this to a user-defined class? i.e. if I say

    foo = Click(position=(x, y))

    ...
    case Click(position=(x, y))

those identical expressions, for the same value of Click, have widely different semantics?

edit: typo fix

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Re:Pattern matching accepted for Python by bobbylarrybobby on Wednesday February 10, 2021 @09:54PM (#26097727)

You are (sadly) correct. The latter example checks that the type of `event.get()` is a Click, then that it has a `.position` attribute that be restructured into a two-element tuple `(x,y)`. It's equivalent to `ev = event.get(); if isinstance(ev, Click): (x,y) = ev.position`

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