[Pyparsing] Fwd: Returning an actual `list`

[Athanasios A. <ath...@gm...>]

Hello everyone

Any ideas on the attached?

All the best
AA


---------- Forwarded message ----------
From: Athanasios Anastasiou <ath...@gm...>
Date: Wed, Oct 4, 2017 at 11:44 AM
Subject: Returning an actual `list`
To: pyp...@li...


Hello

I have set up a very simple "primitive data type" parsing system to parse
numbers, quoted strings, lists and dictionaries. The last two are following
Python's convention.

While this is working, I am having trouble returning specific data types
from the "action" of the LIST definition.

Here is a snippet:

LIST = pyparsing.Forward()
DICT = pyparsing.Forward()

VALUE = (NUMBER|IDENTIFIER|DICT|pyparsing.Group(LIST))

KEY_VALUE_PAIR = pyparsing.Group(IDENTIFIER("key") +
pyparsing.Suppress(":") + VALUE("value"))

LIST << pyparsing.Suppress("[") + pyparsing.delimitedList(VALUE) +
pyparsing.Suppress("]")
DICT << pyparsing.Suppress("{") + pyparsing.delimitedList(KEY_VALUE_PAIR) +
pyparsing.Suppress("}")

So, when you are trying to parse something like: [1,2,3,4,[5,6]], this is
returned as a pyparsing.ParseResults type of object, rather than a `list`.
I have tried to set a simple parseAction with `lambda s,l,t: list(t)` or
`lambda s,l,t:list(t[0])` but I am still getting back a ParseResults object.

Ideally, I would like the rule to return a list, just like the INT rule
returns a proper Python integer.

Any ideas about what am I missing?

All the best
AA