[Python-ideas] Fwd: Define a method or function attributeoutside of a class with the dot operator
steve at pearwood.info
Sat Feb 11 23:10:52 EST 2017
On Fri, Feb 10, 2017 at 06:17:54PM +0200, Markus Meskanen wrote:
> Well yes, but I think you're a bit too fast on labeling it a mistake to use
> monkey patching...
More importantly, I think we're being a bit too quick to label this
technique "monkey-patching" at all. Monkey-patching (or MP for brevity)
implies making modifications to some arbitrary *uncooperative* class (or
instance). When you're plugging electrodes into a monkey's brain, the
monkey has no say in it.
This proposed syntax can, of course, be used that way, but Python is
already a "consenting adults" language and already has setattr:
setattr(some_class, 'get_shrubbery', get_shrubbery)
which is all you need to enable MP for good or evil.
There have been a few times where I would have used this syntax if it
had been available, and none of them were MP. They were injecting
methods into classes I controlled.
I suspect that this technique wouldn't feel so bad if we had a proper,
respectable sounding "design pattern" name for it, like "method
injection" or something. I expect that the only reason there is no name
for this is that Java doesn't allow it. (I think.) So I'm going to call
it "method injection".
I don't think there's any evidence that slightly cleaner syntax for
method injection will encourage MP. We already have clean syntax to
inject arbitrary attributes (including methods made with lambda):
TheClass.method = lambda self: ...
and I don't think there's an epidemic of MP going on.
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