[Python-Dev] A usability argument for list-after-def (original) (raw)

Gregory Lielens gregory.lielens at fft.be
Thu Aug 5 23:52:26 CEST 2004

Of the options on the Wiki page ( at http://www.python.org/moin/PythonDecorators ), this seems to leave only list-after-def, the previous community favorite and the first PEP 318 syntax to have been implemented.

Guido's principal argument against list-after-def, if I recall correctly, was that it is ugly when multiple or lengthy decorators are involved. But, "ugly" isn't an argument any more, so that shouldn't rule out list-after-def. :)

On a cosmetic point of view, I also prefer the list-after-def syntax, first time I saw it it was the one than seemed the easiest (the "def f() as [decorator]" variant was event clearer, but the argument that as is only for renaming has mitigaed that somewhat ;-) ) "Cosmetic" does not sound like a very convincing argument, but I feel that this whole discussion is purely on a cosmetic level anyway, it is just a way to express more clearly something that is already possible...and as feedback as been asked for... ;-)

But does it means that the list-after-def behaves like all lists, so that these are possible and equivalent?

def foo() [decorator1, decorator2(bar)]: ...

def foo() [ decorator1, decorator2(bar)]: ...

my_complex_decorator=[decorator1, decorator2(bar)] def foo() my_complex_decorator : ...

If it is, I am +1 on list-after-def (and, because of the last example, +2 on a variant with a keyword or pseudo-keyword between the def and the list, like ("with" is only an example) :

def foo() with [decorator1, decorator2(bar)]: ... my_complex_decorator=[decorator1, decorator2(bar)] def foo() with my_complex_decorator : ... def foo2() with my_complex_decorator : ...

If not (i.e. the brackets are just a syntax hint), I am -1, I prefer the the pie syntax cause it would break consistency with other lists usage... For example, for j in [1,2]: ... for j in ["a","b", 1,2,3,4]: ... for j in mylist: ... are all possible, so it would be very surprising if the def syntax would not be similar, it would mean that the brackets after a def are not really a list and that would feel too much like special-casing to me...

Best regards,

Greg.

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