Underscore data hiding (was python development practices?)
Russell E. Owen
owen at astrono.junkwashington.emu
Wed Oct 31 18:15:38 CET 2001
In article <ddluttodf5dctdk9gk5900dqc158oo448o at 4ax.com>,
Peter Wang <pzw1 at cor-no-spam-nell.edu> wrote:
>On 30 Oct 2001 17:11:28 -0800, Paul Rubin <phr-n2001d at nightsong.com>
>>Peter Wang <pzw1 at cor-no-spam-nell.edu> writes:
>>> while i feel that Python makes me far more productive as a programmer
>>> for all the projects on which i've worked, i'm inclined to agree that
>>> the lack of data hiding coupled with lack of a standard interface
>>> specification would cause problems in a team.
>>Well, there's cheesy data hiding in the sense that instance variables
>>whose names begin with underscores are difficult to reach from other
>well... kind of. but short of naming all my private variables "_foo"
>and hacking around the problem, there's no way to prevent lazy
>programmers from touching all of your classes's data members. i know
>this is not python's paradigm, but OTOH this is something that has to
>be dealt with in a production environment...
This brings up an issue about using underscore to hide data...
My understanding is that a double underscore is required for Python to
automagically mangle the name. On the other hand, two postings now
suggest that a single underscore is sufficient.
If double underscore is required, then it seems to me this is a very
common misconception that a single is sufficient. It might be worth
If double is not required, I'd love to know about it. Single looks a lot
neater, and I'm not fond of double punctuation symbols that are hard to
Personally, I'd like to see the variable mechanism made more explicit
and robust, including:
- an explicit way to declare class instance variables as hidden
- a means of explicitly declaring variables (e.g. a "local" keyword),
- a way to turn on checking for undeclared variables (e.g. a pragma-like
mechanism, so it can be applied to modules)
- a way to turn off the ability to add new instance variables to class
instances (something really simple and obvious, such as a pragma)
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