extending file?

[Chris Cioffi]

Hello all,

Are there any docs or examples of extending the file type? I work
with EDI messages that are very like text files, just with a few
quirks. ;-) and I was wondering if I could strech and twist the built
in file type to make things a bit faster and more full featured.

Specifically I would need to alter the iterator and ideally the line terminitor.

Chris
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[Diez B. Roggisch]

Re: extending file?

Chris Cioffi wrote:
[color=blue]
> Are there any docs or examples of extending the file type? I work
> with EDI messages that are very like text files, just with a few
> quirks. ;-) and I was wondering if I could strech and twist the built
> in file type to make things a bit faster and more full featured.[/color]

I'm not sure what you want to accomplish here - but one of the nicer aspects
of python is that you don't have to inherit from file when you want to pass
a file-like object to some lib. See the cStringIO module. So if you create
a edi-class that _behaves_ like a file, thats all you need - you then can
pass it to any file-accepting pieco of code.

Is that what you've been asking for?
--
Regards,

Diez B. Roggisch

[Bengt Richter]

Re: extending file?

On Tue, 02 Nov 2004 12:13:34 -0500, Jeremy Jones <zanesdad@bells outh.net> wrote:
[color=blue]
><snip the whole thread>
>
>So, with everything being said that's been said, here's are two
>questions for myself and for Chris Cioffi:
>
>1. How difficult would it be to modify file.readline() so it would read
>until a specific character rather than the standard end of line
>character(s) ?
>2. What would be the best way to go about the above?
>
>If anyone has any ideas, I think we would both listen with great interest.
>
>[/color]
Maybe this general idea could give you a way to install your own custom solution
without an app-specific custom mod to file or open:

I'd like to see a file/open hook in sys (or maybe os), so that you could intercept the open
operation for specific file paths registered with the hook. E.g., if it were a
simple directory

sys.filehook['foo.txt'] = MyFileClass # or callable factory

would cause file('foo.txt', mode, kwarg=something ) to look in sys.filehook before going to the normal
file system, and return MyFileClass('fo o.txt', mode, kwarg) instead of the normal file object. (I.e.,
file & open would be extended to accept *args, **kw to pass through to hooks if present)

This would allow passing custom input sequences as file-like objects to programs whose interface
is a file path string, and obviously you could use the file path arg passed through to open/file
to open a real file that you wanted to filter in some way (assuming you temporarily at least
removed the hook, or had an alias to the unhooked open function).

I don't think this would be hard to implement, but I haven't thought it through.
Gotta go vote. And other stuff...

An extension of this idea would be to allow registering patterns like
sys.filehook['*.cfg'] = MyConfigFilter
where a mathing open would pass through the actual matched path.


Regards,
Bengt Richter