A rough first translation of Jesse's BNF grammar into pyparsing

ingredientparser.py

from string import lowercase, uppercase
from pyparsing import (Word, Literal, ZeroOrMore, Regex, Or, CharsNotIn,
					   Optional, CaselessLiteral, Combine, Suppress,
					   srange, alphas, alphanums, nums)

def Literals(s, splitchar=None):
	"""Splits the given string (defaults to splitting on spaces), turns each
	item into a Literal, and combines them into an Or clause."""
	return Or(map(Literal, s.split(splitchar)))

ess = Literal('es') | Literal('s')
alphanum = Word(alphanums + "',/.-")
alpha = Word(alphas + "'-")
num = Word(nums)
numword = Literals('one two three four five six seven eight nine ten')
fractional = Literals('half third fourth fifth sixth')
dot = Literal('.')
range_ = Literals('to -')
comma = Literals(', -')
connector = Literal('of')
paren = Literals('( )')

containers = Combine(Literals('package pk bag can container cn envelope jar')
					 + Optional(ess))
metric = Literals('kg gram kilogram kg ml liter cc')
colloq = Literals("dozen/half-dozen/half dozen/doz/ea/each/x/"
                  "baker's dozen/bakers dozen/","/")
relative = Literals('medium-sized medium med/small med large small s lg')
genus = Literals('bunch bn head clove ear batch slice stick leg zest rind '
				 'sprig')
imperial = Literals('feet cup c quart qt pint teaspoon tspn tsp tablespoon '
					'tbsp tb ts t pound lb ounce oz gallon')
mod_amount = Literals('scant generous several about')
qualitative = Literals('dash ds pinch pn splash shake')

fraction_word = numword + Combine(fractional + Optional(ess))
fraction = Combine(num + '/' + num, adjacent=False)
numeral = num + Optional(dot + num)
mixed = Combine(numeral + fraction, adjacent=False, joinString=' ')
word_mixed = numword + (fraction ^ fraction_word)
sub_amount = mixed ^ fraction ^ numeral ^ fraction_word ^ numword
amount = sub_amount + Optional(range_ + sub_amount).setResultsName('amount')

c1 = ((Optional(paren) + amount) ^
	  (comma + relative) ^
	  metric ^
	  (imperial + Optional(dot)) ^
	  (comma + containers + Optional(paren)))
container = c1 ^ containers

measurement = Combine(
	Optional(mod_amount) +
	(container ^ relative ^ metric ^ imperial ^ colloq ^ genus ^ qualitative) +
	Optional(dot) + Optional(ess), adjacent=False).setResultsName('measurement')

words = alpha + ZeroOrMore(alpha)
words_plus = alphanum + ZeroOrMore(alphanum)
paren_comment = "(" + words_plus + ")"
comment = paren_comment ^ words_plus
thing = (Optional(words) + paren_comment + words) ^ words
anything = Regex('.*').setResultsName('anything')

list_ = Optional(Literal('*')) ^ Literal('the')
fork = Literals("plus or and")
suffix = CharsNotIn('\r\n')
about = CaselessLiteral('about')

type1 = Suppress(Optional(about)) + amount + measurement + anything
type2 = measurement + anything
type3 = Suppress(Optional(about)) + amount + anything

ingredient = Optional(list_) + (type1 ^ type2 ^ type3)

print ingredient.parseString('three jars of dozen eggs')

##############################################################################
# Original grammar by Jesse, from keycore/recipes/utils/parser.py
##############################################################################
"""
<nl>			:= [\n\r]+
<ts>			:= [ \t]+
ess				:= ('es'/'s')
alphanum		:= [A-Za-z',/0-9.-]+
alpha			:= [A-Za-z'-]+
numword			:= ('one'/'two'/'three'/'four'/'five'/'six'/'seven'/'eight'/'nine'/'ten')
dot				:= "."
range			:= ('to'/'-')
<comma>			:= [,-]+
connector		:= 'of'
paren			:= ('('/')')

containers		:= ('package'/'pk'/'bag'/'can'/'container'/'cn'/'envelope'/'jar'),ess?
metric			:= ('kg'/'gram'/'kilogram'/'ml'/'liter'/'cc')
colloq			:= ('dozen'/'half-dozen'/'half dozen'/'bakers dozen'/'doz'/'ea'/'each'/'x')
relative		:= ('medium-sized'/'medium'/'med/small'/'med'/'large'/'small'/'s'/'lg')
genus			:= ('bunch'/'bn'/'head'/'clove'/'ear'/'batch'/'slice'/'stick'/'leg'/'zest'/'rind'/'sprig')
imperial		:= ('feet'/'cup'/'c'/'quart'/'qt'/'pint'/'teaspoon'/'tspn'/'tsp'/'tablespoon'/'tbsp'/'tb'/'ts'/'t'/'pound'/'lb'/'ounce'/'oz'/'gallon' )
mod_amount		:= ('scant'/'generous'/'several'/'about')
qualitative		:= ('dash'/'ds'/'pinch'/'pn'/'splash'/'shake')
fraction_word	:= numword,ts,('half'/'third'/'forth'/'fifth'/'sixth'),ess?
fraction		:= [0-9]+,"/",[0-9]+
numeral			:= [0-9]+,(dot,[0-9]+)?
mixed			:= numeral,ts,(fraction/fraction_word)
word_mixed		:= numword,ts,(fraction/fraction_word)
sub_amount		:= (mixed/fraction/numeral/fraction_word/numword)
amount			:= (sub_amount,ts?,range,ts?,sub_amount)/sub_amount

c1				:= (paren?,amount,ts/comma,relative/metric/imperial,dot?,ts/comma,containers,paren?)
#c2				:= (containers,ts?,paren,amount,comma/ts,relative/metric/imperial,dot?,paren)
container		:= (c1/containers)

measurement		:= (mod_amount, ts)?,(container/relative/metric/imperial/colloq/genus/qualitative),dot?,ess?

words			:= alpha,(ts,alpha,?-('in'/'or'))*
words_plus		:= alphanum,(ts,alphanum)*
paren_comment	:= "(",ts?,words_plus,ts?,")"
comment			:= paren_comment/words_plus
thing			:= (words?,paren_comment,words)/words
any				:= [.]*

<list>			:= ([*]/'the')
fork			:= ('plus'/'or'/'and')
suffix			:= [^\n\r]+
ingredient		:= list?,ts?,(type2/type1/type3)
type1			:= measurement,ts,any
type2			:= ('about',ts)?,amount,ts?,measurement,ts,any
type3			:= ('about',ts)?,amount,ts,any
"""

if __name__ == '__main__':
	import doctest

	tests = [
		('1 onion', ['1', 'onion']),

		]