Why isn’t there a copy() method in Sequence and MutableSequence ABCs?

Interesting thought! When crafting an interface, implementing a method like `copy()` puts a lot of responsibility on the implementer, which could lead to bloating the interface with methods that may not be necessary for all implementations. The focus here is on ensuring the interface stays clean and not every sequence needs a `copy()` method. Plus, developers can still add whatever extra methods they like if they need that functionality!

From what I've gathered, the goal was to keep the interface as minimal as possible. A collection can function just fine without a `copy()` method, so it seems like the designers wanted to avoid adding unnecessary complexity. While it seems like `list`, `dict`, and `set` include `copy()` and other methods, it makes sense to have a streamlined interface for something foundational like `Sequence`. Pretty good question, by the way!

Absolutely! It's funny how using `copy` can sometimes over-complicate things. I think Guido's idea of just using `list(x)` instead of `x.copy()` highlights this well. The `list()` function makes it clear what the output type is going to be, while `x.copy()` might add confusion about the underlying type. I've been teaching my students similar concepts, so it’s nice to see I’m not the only one.

That's an intriguing way to look at it! I suppose if we start asking why certain behaviors are enforced, we open up a whole discussion about the potential implementations of sequences, even ones that are hardware-driven. It definitely adds a layer of complexity when you think about what 'copying' really means in various contexts.

Great point! Abstract base classes (ABCs) are primarily about making sure that classes implement a minimal set of features to be classified as a certain type of collection. This acts like a safety net for interfaces without the formal type structures you'd see in some other languages. If a type checker knows an object is a `Sequence`, it'll flag errors if you try to mutate it inappropriately, which is super useful for static type checking. Here's a quick example: if you define a `Sequence[str]` and forget that it's not a mutable type, the type checker will catch it for you.