[Python-Dev] Re: copy, len and the like as 'object' methods? (original) (raw)

Paul Prescod paulp@ActiveState.com
Wed, 22 Aug 2001 18:08:40 -0700

Ka-Ping Yee wrote:

... Hmm. And what of, say, abs(-3)? Should that be -3.abs()?

The former is more in-line with traditional mathematical notation. I think that counts for something. And anyhow, abs is not fully polymorphic so it is a little bit of a different case.

Would you also argue for [1, 2, 3].repr() and "abc".hash()?

Yes. But hashing and repring are done much less often than taking the length. So I wouldn't worry about them...in this round anyhow. Plus repr has a first-class syntax so the function is kind of redundant already!

Where do you draw the line?

If a function takes a single argument that is a Python object and immediately dispatches to a magic method, and it is "important" enough to be a builtin, then it should probably just be a method. What is the point of hiding what is really going on -- a method call!

Maybe my habits are too ingrained at this point, but i kind of like the boundary between methods and ordinary methods... it would somehow bug me to have all these methods like abs, len, hash crowding in on my ordinary-method namespace.

I can appreciate that your tastes are different from mine...in fact I said something similar to David when he first suggested it to me but on reflection it seemed such a subtle thing when compared against the weirdness of the definition of len:

def len(obj): return obj.length()

It does a little bit more but not much! If you put that in a module you wrote you would consider it a little bit bizarre, useless and confusing. Plus it is another indirection which saps a tiny bit of performance for nothing.

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