53 lines
1.9 KiB
Plaintext
53 lines
1.9 KiB
Plaintext
From: donn at u.washington.edu (Donn Cave)
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Date: 26 Apr 1999 16:40:25 GMT
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Subject: Emulating C++ coding style
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References: <371F8FB7.92CE674F@pk.highway.ne.jp> <371F9D0C.4F1205BB@pop.vet.uu.nl> <7foe7r$15mi$1@nntp6.u.washington.edu> <37245184.3AADF34D@pop.vet.uu.nl>
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Message-ID: <7g24tp$raa$1@nntp6.u.washington.edu>
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Content-Length: 1536
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X-UID: 22
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Martijn Faassen <faassen at pop.vet.uu.nl> writes:
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| Donn Cave wrote:
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...
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|> It's not much like C++ here, but it's uncanny how it reeks of Python!
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|> Namespaces, references!
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| Indeed. Not having used that class attribute trick often myself, I
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| wasn't aware of this surprising behavior. I suppose in order to get the
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| C++ behavior it's best to use a module global variable.
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Not at all, either way is fine - the class scope is just as good a place
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as the module scope, for me it's the perfect place for things that are
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specific to the class.
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It's the usage that you have to watch out for, and while there are some
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perils for the unwary, in the long run it's also an opportunity to gain
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a deeper understanding of how simple Python is. Same for module attributes -
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common problem, someone imports a module attribute like
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from foo import shared
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shared = 5
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and then wonders, how come no change to the attribute as seen from other
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modules. The right way to set to a module attribute - if you must do this
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at all - is
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foo.shared = 5
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and just the same for a class attribute (of class Foo):
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from foo import Foo
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Foo.shared = 5
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In general, you have the problem only when your usage doesn't reflect the
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design. If it's really a class attribute, but you set it in the instance
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scope, if it's really an external module attribute but you bind it into
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the present module's scope during import. Python bites if you trick it.
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Donn Cave, University Computing Services, University of Washington
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donn at u.washington.edu
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