[Pyparsing] How to distinguish a variable from a integer

[Gustavo N. <me...@gu...>]

Hello, everybody.

First of all, I wanted to thank you for this awesome package. I'm having fun 
with it. :)

I've read O'reilly's shortcut on Pyparsing, but still I can't find an answer 
to this:

One of the components of the grammar I'm defining is an operand. Operands can 
be a number or a variable. A variable is a string made up of word characters 
(in any language), numbers (in any language/culture) and/or a spacing 
character (underscores by default).

I'm using the following:
"""
import re
from pyparsing import *

# Defining the numbers:
decimal_sep = Literal(".")
decimals = Optional(decimal_sep + OneOrMore(Word(nums)))
number = Combine(Word(nums) + decimals)

# Defining the variables:
variable = Regex("[\w\d_]+", re.UNICODE)

# Finally, let's define the operand:
operand = number | variable
"""

The operand above works perfectly with the following expressions:
hello -> variable
23 -> number
hello_world -> variable

But it doesn't support variables which begin with a number (e.g., 
"1st_variable"). I get the following exception all the time:
>>>> from varnums import *
>>>> operand.parseString("1st_variable")
>(['1'], {})
>>>> operand.parseString("1st_variable", parseAll=True)
>Traceback (most recent call last):
>  File "<stdin>", line 1, in <module>
>  File
> "/home/gustavo/System/pyenvs/booleano/lib/python2.6/site-packages/pyparsing
>-1.5.2-py2.6.egg/pyparsing.py", line 1076, in parseString raise exc
>pyparsing.ParseException: Expected end of text (at char 1), (line:1, col:2)


I know I can invert the definition of the operand (i.e., "operand = variable | 
number"), but then strings like "22" will be matched as variables (not 
numbers).

How can I fix this?

Thanks in advance.
-- 
Gustavo Narea <xri://=Gustavo>.
| Tech blog: =Gustavo/(+blog)/tech  ~  About me: =Gustavo/about |