[Python-Dev] PEP 318: More examples of decorator use (original) (raw)

Phillip J. Eby pje at telecommunity.com
Tue Apr 6 19:43:08 EDT 2004

At 03:08 PM 4/6/04 -0700, Jim Hugunin wrote:

*Some examples that I'd like to see in an anti-patterns list

onexit from the PEP. I don't think decorators should have side-effects visible outside of the class/function itself. This seems MUCH better accomplished with the explicit call to the registration function. singleton from the PEP. Whenever possible, decorators should return the same kind of thing that they are given. This code seems much less clear than explicitly creating a singleton instance. propget, propset, propdel from Edward Loper via Guido. To me, these violate the principle of modularity. I much prefer the explicit property declaration that puts all of the parts together. class C(object): _def getX(self): return self.x _def setX(self, x): self.x = x x = property(getX, setX)

Hm. IIRC, Visual Basic defines "property set", "property let", and "property get" methods in a similar fashion to the propget/propset/propdel mechanism. What does C# use? Doesn't it have such methods also?

Also, most languages that I've encountered that offer generic functions, signature overloading, or other similar dispatch mechanisms use variations of defining the same function/method over and over again, each variation with the same name, just a different signature, matching pattern, etc.

A bigger problem with propget et al is that they don't follow a sensible inheritance mechanism. That is, you can't inherit the get method while overriding the set method. But this is really more a limitation of the way Python descriptors work, than any issue with decorators.

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