[Pyparsing] Lists and Groups

[Michael F. <nob...@gm...>]

Hello all,

First, thanks for the wonderful programming API. I'm having a long of fun
with it.

I have a question, I feel like I'm ruining the BNF expression when overly
massage the input. Should I stick to BNF or start tokenizing? Allow me to
explain.

I've always been fascinated with interfaces which seem to understand human
language, kind of like gmail's "quick-add" featurer for its calender.

So, to learn how to do this better, I'm writing a little diddy to interpret
simple commands into creating a shopping list. Here is a list of generic
input I expect it to understand


#test grammar
tests= """\ buy chocolate milk, eggs and bread at store
    get eggs at @Vons
    need headache medicine and cough medicine from downtown drug store
    buy nails, claw hammer, and studs at @homedepot
    buy ragjoint at car parts store
    buy laptop at electronics store
    get candy @Sees
    get a clue""".splitlines()

My evil mashup is as follows...

# define grammar
KW = Keyword
and_ = Literal(" and ")
comma = Literal(",")
at = KW("from") | KW("at")
label = Literal("@") + Word(alphanums)
buy = KW("buy") | KW("get") | KW("need")
item = Group( OneOrMore( ~ (at | and_) + (Word(alphas + "-"))) +
Suppress(Optional(comma))) | Suppress(Optional(and_))
items = Group( OneOrMore( item ) )
store = KW("store") | KW("market") | KW("grocery")
storetype = Suppress(at) + Group(OneOrMore( Word(alphas)))
storelabel = label
storename = storetype | storelabel
shlisti = Suppress(buy) + items + Optional( storename )

What I wish to do is interpret a sentence starts with some synonym of "buy",
interprets everything after that as a list of things to buy (accepting and
as a synonym for a comma) until it reaches some synonym of "from", and then
everything after that is interpreted as a store name. All I want to keep is
the list of items, and the storename.

What I wind up doing is as follows:

buy chocolate milk, eggs and bread at store -> [[['chocolate', 'milk']]]
get eggs at @Vons -> [[['eggs']]]
need headache medicine and cough medicine from downtown drug store ->
[[['headache', 'medicine', 'and', 'cough', 'medicine']], ['downtown',
'drug', 'store']]
buy nails, claw hammer, and studs at @homedepot -> [[['nails']]]
buy ragjoint at car parts store -> [[['ragjoint']], ['car', 'parts',
'store']]
buy laptop at electronics store -> [[['laptop']], ['electronics', 'store']]
get candy @Sees -> [[['candy']], '@', 'Sees']
get a clue -> [[['a', 'clue']]]

Is there a way to express it in the nice BNF form or did I already jump off
that reservation with the grouping and suppressing?