Re: [Pyparsing] Grouping when using asList()

[Paul M. <pa...@al...>]

Joshua -

You already had most of the pieces there, just a couple of gaps around a
little-used feature.

>>>One question: ("defs") is a call to what Groups() returns, but I'm not
following. Can you point me to something in the docs that explains what is
done when you call a pyparsing expression?<<<

Let's say you have this form for a date string:

twoDigitInt = Word(nums,exact=2)
date = twoDigitInt + '/' + twoDigitInt + '/' + twoDigitInt

The old way to assign results names was (I'm using US date format mm/dd/yy
convention):

date = twoDigitInt.setResultsName("month") + '/' +
twoDigitInt.setResultsName("day") + '/' + twoDigitInt.setResultsName("year")

I *really* wanted to encourage people to use results names, so I made
ParserElements "callable", and having the __call__ function call
setResultsName, thus supporting the following shortened syntax:

date = twoDigitInt("month") + '/' + twoDigitInt("day") + '/' +
twoDigitInt("year")

Try to look past the "it's a function call" to "this is a lot easier to
specify a results name than that old way!".  (However, if you need to add
the listAllMatches attribute, this still requires the explicit call to
setResultsName.)

I hope that's not too confusing.

-- Paul