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]> 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():
dumpEntries(dct[k][0],depth+1)
else:
print dct[k][0]
else:
print dct[k]
dumpEntries( parsedEntries )
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
--
'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.'
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