Liam - I just uploaded an update to pyparsing, version 1.3.2, that should fix the problem with using nested Dicts. Now you won't need to use [0] to dereference the "0'th" element, just reference the nested elements as a.b.c, or a["b"]["c"].
-- Paul -----Original Message----- From: Liam Clarke [mailto:[EMAIL PROTECTED] Sent: Sunday, July 24, 2005 10:21 AM To: Paul McGuire Cc: tutor@python.org Subject: Re: [Tutor] Parsing problem Hi Paul, That is fantastic. It works, and using that pp.group is the key with the nested braces. I just ran this on the actual file after adding a few more possible values inside the group, and it parsed the entire header structure rather nicely. Now this will probably sound silly, but from the bit header = {... ... } it continues on with province = {... } and so forth. Now, once it reads up to the closing bracket of the header section, it returns that parsed nicely. Is there a way I can tell it to continue onwards? I can see that it's stopping at one group. Pyparsing is wonderful, but boy... as learning curves go, I'm somewhat over my head. I've tried this - Code http://www.rafb.net/paste/results/3Dm7FF35.html Current data http://www.rafb.net/paste/results/3cWyt169.html assignment << (pp.OneOrMore(pp.Group( LHS + EQUALS + RHS ))) to try and continue the parsing, but no luck. I've been running into the File "c:\python24\Lib\site-packages\pyparsing.py", line 1427, in parseImpl raise maxException pyparsing.ParseException: Expected "}" (at char 742), (line:35, col:5) hassle again. From the CPU loading, I'm worried I've got myself something very badly recursive going on, but I'm unsure of how to use validate() I've noticed that a few of the sections in between contain values like this - foo = { BAR = { HUN = 10 SOB = 6 } oof = { HUN = { } SOB = 4 } } and so I've stuck pp.empty into my RHS possible values. What unintended side effects may I get from using pp.empty? From the docs, it sounds like a wildcard token, rather than matching a null. Using pp.empty has resolved my apparent problem with empty {}'s causing my favourite exception, but I'm just worried that I'm casting my net too wide. Oh, and, if there's a way to get a 'last line parsed' value so as to start parsing onwards, it would ease my day, as the only way I've found to get the whole thing parsed is to use another x = { ... } around the whole of the data, and now, I'm only getting the 'x' returned, so if I could parse by section, it would help my understanding of what's happening. I'm still trial and error-ing a bit too much at the moment. Regards, Liam Clarke On 7/24/05, Paul McGuire <[EMAIL PROTECTED]> wrote: Liam - Glad you are sticking with pyparsing through some of these idiosyncracies! One thing that might simplify your life is if you are a bit more strict on specifying your grammar, especially using pp.printables as the character set for your various words and values. Is this statement really valid? Lw)r*)*dsflkj = sldjouwe)r#jdd According to your grammar, it is. Also, by using printables, you force your user to insert whitespace between the assignment target and the equals sign. I'm sure your users would like to enter a quick "a=1" once in a while, but since there is no whitespace, it will all be slurped into the left-hand side identifier. Let's create two expressions, LHS and RHS, to dictate what is valid on the left and right-hand side of the equals sign. (Well, it turns out I create a bunch of expressions here, in the process of defining LHS and RHS, but hopefullly, this will make some sense): EQUALS = pp.Suppress ("=") LBRACE = pp.Suppress("{") RBRACE = pp.Suppress("}") identifier = pp.Word(pp.alphas, pp.alphanums + "_") integer = pp.Word(pp.nums+"-+", pp.nums) assignment = pp.Forward() LHS = identifier RHS = pp.Forward().setName("RHS") RHS << ( pp.dblQuotedString ^ identifier ^ integer ^ pp.Group( LBRACE + pp.OneOrMore(assignment) + RBRACE ) ) assignment << pp.Group( LHS + EQUALS + RHS ) I leave it to you to flesh out what other possible value types can be included in RHS. Note also the use of the Group. Try running this snippet with and without Group and see how the results change. I think using Group will help you to build up a good parse tree for the matched tokens. Lastly, please note in the '<<' assignment to RHS that the expression is enclosed in parens. I originally left this as RHS << pp.dblQuotedString ^ identifier ^ integer ^ pp.Group( LBRACE + pp.OneOrMore(assignment) + RBRACE ) And it failed to match! A bug! In my own code! The shame... This fails because '<<' has a higher precedence then '^', so RHS only worked if it was handed a quoted string. Probably good practice to always enclose in quotes the expression being assigned to a Forward using '<<'. -- Paul -----Original Message----- From: Liam Clarke [mailto: [EMAIL PROTECTED] Sent: Saturday, July 23, 2005 9:03 AM To: Paul McGuire Cc: tutor@python.org Subject: Re: [Tutor] Parsing problem *sigh* I just read the documentation more carefully and found the difference between the | operator and the ^ operator. Input - j = { line = { foo = 10 bar = 20 } } New code sel = pp.Forward () values = ((pp.Word(pp.printables) + pp.Suppress("=") + pp.Word(pp.printables)) ^ sel) sel << (pp.Word(pp.printables) + pp.Suppress("=") + pp.Suppress("{") + pp.OneOrMore(values) + pp.Suppress("}")) Output - (['j', 'line', 'foo', '10', 'bar', '20'], {}) My apologies for the deluge. Regards, Liam Clarke On 7/24/05, Liam Clarke < [EMAIL PROTECTED] <mailto:[EMAIL PROTECTED]> > wrote: Hmmm... just a quick update, I've been poking around and I'm obviously making some error of logic. Given a line - f = "j = { line = { foo = 10 bar = 20 } }" And given the following code - select = pp.Forward() select << pp.Word(pp.printables) + pp.Suppress("=") + pp.Suppress("{") + pp.OneOrMore ( (pp.Word(pp.printables) + pp.Suppress("=") + pp.Word(pp.printables) ) | select ) + pp.Suppress("}") sel.parseString(f) gives - (['j', 'line', '{', 'foo', '10', 'bar', '20'], {}) So I've got a bracket sneaking through there. Argh. My brain hurts. Is the | operator an exclusive or? Befuddled, Liam Clarke On 7/23/05, Liam Clarke < [EMAIL PROTECTED] > wrote: Howdy, I've attempted to follow your lead and have started from scratch, I could just copy and paste your solution (which works pretty well), but I want to understand what I'm doing *grin* However, I've been hitting a couple of ruts in the path to enlightenment. Is there a way to tell pyparsing that to treat specific escaped characters as just a slash followed by a letter? For the time being I've converted all backslashes to forwardslashes, as it was choking on \a in a file path. But my latest hitch, takes this form (apologies for large traceback) Traceback (most recent call last): File "<interactive input>", line 1, in ? File "parse.py", line 336, in parse parsedEntries = dicts.parseString(test_data) File "c:\python24\Lib\site-packages\pyparsing.py", line 616, in parseString loc, tokens = self.parse( instring.expandtabs(), 0 ) File "c:\python24\Lib\site-packages\pyparsing.py", line 558, in parse loc,tokens = self.parseImpl( instring, loc, doActions ) File "c:\python24\Lib\site-packages\pyparsing.py", line 1518, in parseImpl return self.expr.parse( instring, loc, doActions ) File "c:\python24\Lib\site-packages\pyparsing.py", line 558, in parse loc,tokens = self.parseImpl( instring, loc, doActions ) File "c:\python24\Lib\site-packages\pyparsing.py", line 1367, in parseImpl loc, exprtokens = e.parse( instring, loc, doActions ) File "c:\python24\Lib\site-packages\pyparsing.py", line 558, in parse loc,tokens = self.parseImpl( instring, loc, doActions ) File "c:\python24\Lib\site-packages\pyparsing.py", line 1518, in parseImpl return self.expr.parse( instring, loc, doActions ) File "c:\python24\Lib\site-packages\pyparsing.py", line 560, in parse raise ParseException, ( instring, len(instring), self.errmsg, self ) ParseException: Expected "}" (at char 9909), (line:325, col:5) The offending code can be found here (includes the data) - http://www.rafb.net/paste/results/L560wx80.html It's like pyparsing isn't recognising a lot of my "}"'s, as if I add another one, it throws the same error, same for adding another two... No doubt I've done something silly, but any help in finding the tragic flaw would be much appreciated. I need to get a parsingResults object out so I can learn how to work with the basic structure! Much regards, Liam Clarke On 7/21/05, Paul McGuire < [EMAIL PROTECTED] <mailto:[EMAIL PROTECTED]> > wrote: Liam, Kent, and Danny - It sure looks like pyparsing is taking on a life of its own! I can see I no longer am the only one pitching pyparsing at some of these applications! Yes, Liam, it is possible to create dictionary-like objects, that is, ParseResults objects that have named values in them. I looked into your application, and the nested assignments seem very similar to a ConfigParse type of structure. Here is a pyparsing version that handles the test data in your original post (I kept Danny Yoo's recursive list values, and added recursive dictionary entries): -------------------------- import pyparsing as pp listValue = pp.Forward() listSeq = pp.Suppress ('{') + pp.Group(pp.ZeroOrMore(listValue)) + pp.Suppress('}') listValue << ( pp.dblQuotedString.setParseAction(pp.removeQuotes) | pp.Word(pp.alphanums) | listSeq ) keyName = pp.Word( pp.alphas ) entries = pp.Forward() entrySeq = pp.Suppress('{') + pp.Group(pp.OneOrMore(entries)) + pp.Suppress('}') entries << pp.Dict( pp.OneOrMore ( pp.Group( keyName + pp.Suppress('=') + (entrySeq | listValue) ) ) ) -------------------------- Dict is one of the most confusing classes to use, and there are some examples in the examples directory that comes with pyparsing (see dictExample2.py), but it is still tricky. Here is some code to access your input test data, repeated here for easy reference: -------------------------- testdata = """\ country = { tag = ENG ai = { flags = { } combat = { DAU FRA ORL PRO } continent = { } area = { } region = { "British Isles" "NorthSeaSea" "ECAtlanticSea" "NAtlanticSea" "TagoSea" "WCAtlanticSea" } war = 60 ferocity = no } } """ parsedEntries = entries.parseString(testdata) def dumpEntries(dct,depth=0): keys = dct.keys() keys.sort() for k in keys: print (' '*depth) + '- ' + k + ':', if isinstance(dct[k],pp.ParseResults): if dct[k][0].keys(): print dumpEntries(dct[k][0],depth+1) else: print dct[k][0] else: print dct[k] dumpEntries( parsedEntries ) print print parsedEntries.country[0].tag print parsedEntries.country[0].ai[0].war print parsedEntries.country[0].ai[0].ferocity -------------------------- This will print out: -------------------------- - country: - ai: - area: [] - combat: ['DAU', 'FRA', 'ORL', 'PRO'] - continent: [] - ferocity: no - flags: [] - region: ['British Isles', 'NorthSeaSea', 'ECAtlanticSea', 'NAtlanticSea', 'TagoSea', 'WCAtlanticSea'] - war: 60 - tag: ENG ENG 60 No -------------------------- But I really dislike having to dereference those nested values using the 0'th element. So I'm going to fix pyparsing so that in the next release, you'll be able to reference the sub-elements as: print parsedEntries.country.tag print parsedEntries.country.ai.war print parsedEntries.country.ai.ferocity This *may* break some existing code, but Dict is not heavily used, based on feedback from users, and this may make it more useful in general, especially when data parses into nested Dict's. Hope this sheds more light than confusion! -- Paul McGuire _______________________________________________ Tutor maillist - Tutor@python.org <mailto:Tutor@python.org> http://mail.python.org/mailman/listinfo/tutor <http://mail.python.org/mailman/listinfo/tutor> -- 'There is only one basic human right, and that is to do as you damn well please. And with it comes the only basic human duty, to take the consequences.' -- 'There is only one basic human right, and that is to do as you damn well please. And with it comes the only basic human duty, to take the consequences.' -- 'There is only one basic human right, and that is to do as you damn well please. And with it comes the only basic human duty, to take the consequences.' -- 'There is only one basic human right, and that is to do as you damn well please. And with it comes the only basic human duty, to take the consequences.' _______________________________________________ Tutor maillist - Tutor@python.org http://mail.python.org/mailman/listinfo/tutor
