Re: [Pyparsing] How to distinguish a variable from a integer

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

> -----Original Message-----
> From: spir [mailto:den...@fr...]
> You could also add a lookahead for !(letter | '_') trailing after the
> definition of number, but then your definition of variable is unclear. It
> should be required that a variable has at least one non-digit char. Which
> is uneasy ;-)
> 

Yes, Denis has another approach.  You can use parse actions as a way to add
validation logic like Denis suggests.  Here is a validating parse action
that you could attach to variable to ensure that it contains at least one
non-digit.

def mustHaveAtLeastOneNonDigit(tokens):
    if all(c.isdigit() for c in tokens[0]):
        raise ParseException("variable must have at least one non-digit")
variable.setParseAction(mustHaveAtLeastOneNonDigit)


Parse actions can serve a number of uses.  They can also be chained so that
multiple actions or validations can be invoked:


ip_part = Word(nums)
convertToInt = lambda tokens: int(tokens[0])
def validateRange(tokens):
    if not 0 <= tokens[0] < 256:
        raise ParseException("value must be in range 0-255")
ip_part.setParseAction(convertToInt, validateRange)
# or:
# ip_part.setParseAction(convertToInt)
# ip_part.addParseAction(validateRange)
ip_addr = Combine(ip_part + ('.'+ip_part)*3 )

print ip_addr.parseString("192.168.0.255")
print ip_addr.parseString("123.456.789.000")


-- Paul