[Python] Using pyparsing to parse infix expression

I am learning Paul McGuire's fabulous pyparsing Python module. I'm posting this for discussion and hopefully to get a deeper insight into pyparsing.

The following code parses a parenthetical expression that looks similar to a Django Q() object expression used for querying data. Here is an example expression:

'( title__regex=r"^(An?|The) +" ) | ( id__in=[1, 3, 4] )'


Here's the code:

import pyparsing as p

ident = p.Word(p.identchars, p.identbodychars)
cond_op = p.Opt('!') + '='
quoted_string = p.quoted_string
unquoted_string = p.Word(p.string.printable, exclude_chars='()\'"')
rvalue = p.OneOrMore(quoted_string | unquoted_string)
infix_operator = p.one_of('& | ^').set_name('"logical operator"')
whitespace = p.ZeroOrMore(p.White())
expr = p.infix_notation(
p.Combine(ident + whitespace + cond_op + whitespace + rvalue),
[(infix_operator, 2, p.opAssoc.LEFT)]
)

string = '( title__regex=r"^(An?|The) +" ) | ( id__in=[1, 3, 4] )'

try:
results = expr.parse_string(string, parse_all=True).as_list()
except p.ParseException as e:
print(e.explain())
else:
print(results)


The code correctly outputs:

[['title__regex=r"^(An?|The) +"', '|', 'id__in=[1, 3, 4]']]


What other solutions are there?

Is there a better way to express a sequence of unquoted and quoted characters? Here quotes prevent parens from being interpreted as the end or start of a parenthetical expression.

If I mangle the input string by removing the = char, i.e. title__regex r"^(An?|The) +", the parser returns:

(title__regex r"^(An?|The) +") | (id__in=[1, 3, 4])
^
ParseException: Expected "logical operator" term, found 'r' (at char 14), (line:1, col:15)


Why is the parser expecting a "logical operator"? It should be expecting "=".

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