On 7/3/07, Brian <[EMAIL PROTECTED]> wrote:
> On Jul 2, 5:43 pm, "Jon Rosebaugh" <[EMAIL PROTECTED]> wrote:
> > On 7/2/07, Brian <[EMAIL PROTECTED]> wrote:
> > > I should note that this library of existing scripts is quite large,
> > > and attempting to modify them (ie change prints to something else)
> > > would be a bit of work. I DID attempt to go the route of making a
> > > controller return a generator that invokes my initial function,
> > > however this quickly turned into a mess since generators may not
> > > 'return' values, and many of the classes used in these scripts
> > > regularly return values and results of function calls.
> >
> > Steve Yegge talked about this problem (in the generic case, not
> > specific to Pylons or Python) in one of his recent blog posts. I think
> > you may find it to be fascinating
> > reading:http://steve-yegge.blogspot.com/2007/06/rich-programmer-food.html
>
> I've actually read that article before, but not sure how it relates to
> my problem. Unless of course you're just saying that I'm not a good
> pylons/python programmer, which I'd readily admit (thus my comment
> about being new to the arena).
I'm suggesting that your problem could be solved through the use of
what would technically be called a 'compiler'. Situation 3 and
Situation 7 described in that blog post are very similar to your
problem. Half of the work is already done for you, in that Python
ships with several modules that will handle the parsing phase quite
nicely. For example:
>>> compiler.parse("result = a + 5")
Module(None, Stmt([Assign([AssName('result', 'OP_ASSIGN')],
Add((Name('a'), Const(5))))]))
>>> compiler.parse("print signal_value")
Module(None, Stmt([Printnl([Name('signal_value')], None)]))
Once you've done that, you need to figure out what you want to replace
those print statements _with_. Maybe you could call a function, and
the function imports pylons.request and gets the current environ, and
finds an 'output buffer' in the environ somewhere, and appends the
string to that.
Then you just need to convert the AST back into code. Quite a bit of
work has already been done in this area, particularly with relation to
Python 3000. See
http://jeremyhylton.blogspot.com/2006/08/python-3000-translation-strategy.html
for an example of one blog post talking about it.
Of course, if you're content with doing this transformation every time
you load these scripts -- maybe this isn't a performance-critical app
-- you can just run the modified AST as-is.
The end result would be a 'compiler' that compiles your print-using
Python code to non-print-using Python code. It's best really to think
of a compiler as just "any program that converts code from one form to
another' when you're thinking about problem solving, which was the
point of Steve's essay.
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