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From: Mel on 2 Mar 2010 09:26
Roy Smith wrote:
[ ... ]
> Why is it unwise?
>
> The use case is I'm importing a bunch of #define constants from a C header
> file. I've got triples that I want to associate; the constant name, the
> value, and a string describing it. The idea is I want to put in the
> beginning of the module:
>
> declare('XYZ_FOO', 0, "The foo property")
> declare('XYZ_BAR', 1, "The bar property")
> declare('XYZ_BAZ', 2, "reserved for future use")
>
> and so on. I'm going to have hundreds of these, so ease of use, ease of
> maintenance, and niceness of presentation are important.

As long as the header file says what you think it says, you're fine. If you
encounter a file that does "#define sys", then the sys module is forever
masked, and your module can't invoke it. A header file that contains
"#define declare" will be fun.

Mel.


From: Roy Smith on 2 Mar 2010 10:19
On Mar 2, 8:33 am, Steve Holden <st...(a)holdenweb.com> wrote:

> And how important is it to make sure that whatever data your program
> processes doesn't overwrite the actual variable names you want to use to
> program the processing?

Oh, I see what you're saying. You're thinking I was going to machine-
process the C header file and pattern-match the #define statements?
Actually, I was just hand-copying the values, and was looking for a
way to reduce typing.

But, I suppose if I were to machine-process the header files, that
would be a concern. I suppose in that case I would make sure I only
inserted variables which matched a particular pattern (ie, "[A-Z]+_[A-
Z][A-Z0-9]+"). In fact, now that you got me thinking in that
direction...

Somewhat sadly, in my case, I can't even machine process the header
file. I don't, strictly speaking, have a header file. What I have is
a PDF which documents what's in the header file, and I'm manually re-
typing the data out of that. Sigh.

From: Steve Holden on 2 Mar 2010 11:14
Roy Smith wrote:
> On Mar 2, 8:33 am, Steve Holden <st...(a)holdenweb.com> wrote:
>
>> And how important is it to make sure that whatever data your program
>> processes doesn't overwrite the actual variable names you want to use to
>> program the processing?
>
> Oh, I see what you're saying. You're thinking I was going to machine-
> process the C header file and pattern-match the #define statements?
> Actually, I was just hand-copying the values, and was looking for a
> way to reduce typing.
>
> But, I suppose if I were to machine-process the header files, that
> would be a concern. I suppose in that case I would make sure I only
> inserted variables which matched a particular pattern (ie, "[A-Z]+_[A-
> Z][A-Z0-9]+"). In fact, now that you got me thinking in that
> direction...
>
> Somewhat sadly, in my case, I can't even machine process the header
> file. I don't, strictly speaking, have a header file. What I have is
> a PDF which documents what's in the header file, and I'm manually re-
> typing the data out of that. Sigh.
>
Don't worry. Now you have revealed the *real* problem you may well find
there are c.l.py readers who can help! Python can read PDFs ...

regards
Steve
--
Steve Holden +1 571 484 6266 +1 800 494 3119
PyCon is coming! Atlanta, Feb 2010 http://us.pycon.org/
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UPCOMING EVENTS: http://holdenweb.eventbrite.com/

From: John Posner on 2 Mar 2010 11:18
On 3/2/2010 10:19 AM, Roy Smith wrote:
>
> Somewhat sadly, in my case, I can't even machine process the header
> file. I don't, strictly speaking, have a header file. What I have is
> a PDF which documents what's in the header file, and I'm manually re-
> typing the data out of that. Sigh.

Here's an idea, perhaps too obvious, to minimize your keystrokes:

1. Create a text file with the essential data:

XYZ_FOO 0 The foo property
XYZ_BAR 1 The bar property
XYZ_BAZ 2 reserved for future use

2. Use a Python script to convert this into the desired code:

declare('XYZ_FOO', 0, "The foo property")
declare('XYZ_BAR', 1, "The bar property")
declare('XYZ_BAZ', 2, "reserved for future use")

Note:

>>> s
'XYZ_FOO 0 The foo property'
>>> s.split(None, 2)
['XYZ_FOO', '0', 'The foo property']

HTH,
John
From: Carl Banks on 2 Mar 2010 11:49
On Mar 2, 5:21 am, Roy Smith <r...(a)panix.com> wrote:
> In article <mailman.96.1267508316.23598.python-l...(a)python.org>,
>  Chris Rebert <c...(a)rebertia.com> wrote:
>
>
>
> > On Mon, Mar 1, 2010 at 8:27 PM, Roy Smith <r...(a)panix.com> wrote:
> > > >From inside a module, I want to add a key-value pair to the module's
> > > __dict__.  I know I can just do:
>
> > > FOO = 'bar'
>
> > > at the module top-level, but I've got 'FOO' as a string and what I
> > > really need to do is
>
> > > __dict__['Foo'] = 'bar'
>
> > > When I do that, I get "NameError: name '__dict__' is not defined".  Is
> > > it possible to do what I'm trying to do?
>
> > Yes; just modify the dict returned by the globals() built-in function
> > instead.
>
> Ah, cool.  Thanks.
>
> > It's usually not wise to do this and is better to use a
> > separate dict instead, but I'll assume you know what you're doing and
> > have good reasons to disregard the standard advice due to your
> > use-case.
>
> Why is it unwise?


He didn't say it was unwise. He said it's usually not wise.


Carl Banks
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