Re: [Pyparsing] automatic naming of parse results?

[Paul M. <pt...@au...>]

> 
> is it possible to do sth. like .setResultsName globally and automatically?
E.g.:
> 
>     a = pyparsing.Group(b + c)
> 
> could work like:
> 
>     a = pyparsing.Group(b + c).setResultsName("a")
> 

Results names are tricky, but useful.  Part of the nuisance of results names
is the ".setResultsName" syntax, so that is why in 1.4.7 I added support for
code like this:

    a = pyparsing.Group(b + c)("a")

That is, I made all ParserElements callable, and __call__ calls
setResultsName.

Also, despite the leading "set" in "setResultsName", you do know I hope that
this method does an implicit copy, and the copy gets the results name, not
the original.  This is so that you can create a basic expression like
integer, and then use it in multiple places with different names, as in:

integer = Word(nums)
personData = Word(alphas)("name") + integer("age") + integer("salary")

(This actually looks almost like a constructor syntax, which is consistent
with the concept that we are creating new sub-expressions, using the
definition of integer as a prototype.)  But you don't really want integer to
have a results name of "integer", since you need different names for the
different data items, so automatic naming, which seems like a good idea at
first, doesn't hold up - sometimes it would be helpful, but other times it
gets in your way.

If you had a grammar with many sub-expressions, you could do something like
this (where '...' is whatever pyparsing definition you want):

Aexpr = ...
Bexpr = ...
Cexpr = ...
grammar = (Aexpr | Bexpr) + OneOrMore(Cexpr)

for exprName in ("Aexpr Bexpr Cexpr".split()):
    # note that this won't work, since it makes and then discards a copy of
the original
    # locals()[exprName].setResultsName(exprName)

    # have to set the attribute directly, like this
    locals()[exprName].resultsName = exprName

This might be more in line with what you were asking.  I've never set an
expression's results name this way, but I don't see anything wrong with it.

-- Paul