fes.py

from pyparsing import *


class Percent(float):
    def __str__(self):
        return super(Percent, self).__str__() + '%'

    def __repr__(self):
        return super(Percent, self).__repr__() + '%'


number = Word(nums + '.-').setParseAction(lambda s, l, t: float(t[0]))
percent = Word(nums + '.-').setParseAction(lambda s, l, t: Percent(t[0])) + Suppress('%')

operand = percent | number

expr = infixNotation(operand, [
    (oneOf('* /'), 2, opAssoc.LEFT),
    (oneOf('>'), 2, opAssoc.LEFT),
    (oneOf('<'), 2, opAssoc.LEFT),
    (oneOf('<='), 2, opAssoc.LEFT),
    (oneOf('>='), 2, opAssoc.LEFT),
    (oneOf('+ -'), 2, opAssoc.LEFT),
    (oneOf('AND and && &'), 2, opAssoc.LEFT),
    (oneOf('OR or || |'), 2, opAssoc.LEFT),
])

nyamo = OneOrMore(Group(expr + Optional(Suppress("if") + expr) + Suppress(LineEnd())))
code = """
(10 + 5%) * 3 / 5 if 10 > 4 < 10
10 + 1% if 10 > 1
10 + 3% if 10 > 0
10 + 100% * 10
"""
r = nyamo.parseString(code)
print r
for i in r:
    print i, len(i)