[Python-Dev] method decorators (PEP 318) (original) (raw)

Skip Montanaro skip at pobox.com
Sat Mar 27 13:11:40 EST 2004 

Barry> attributes, but decorators can also do the trick in a nasty way:
Barry> 
Barry> def foobar [
Barry>     lambda f: f.author = 'Guido van Rossum',
Barry>     lambda f: f.deprecated = True,
Barry>     classmethod] (self, arg):
Barry>     # Now what?

Alex> Not necessarily all that nasty:

Alex> def foobar [ with_attributes(
Alex>          author="Guido van Rossum",
Alex>          deprecated=True),
Alex>      classmethod] (cls, args):
Alex>          pass

Both cases demonstrate why I don't like the decorator-before-args option. Where are the args? Like I said in an earlier post most of the time I look at a function def wanting a quick reminder how to call it. If the argument list doesn't at least start on the same line as the def I think that will be tougher.

Alex> with a built-in 'with_attributes' equivalent to:

Alex> def with_attributes(f, **kwds):
Alex>      for k, v in kwds.iteritems():
Alex>          setattr(f, k, v)
Alex>      return f

Not quite. It has to be written as a function which returns another function, e.g.:

def attrs(**kwds):
    def decorate(f):
        f.__dict__.update(kwds)
        return f
    return decorate

Skip

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