pyparsing-users

[Pyparsing] Unordered set of expressions

[Russell D. <Rus...@as...>]

I have to parse something with an unordered set of expressions. In the
simplest case, some expressions are required, some are optional. For
this, parsing is easy:

language = expr1 & expr2 & Optional(expr3)

However, there are cases where an expression can occur zero or more
times, one or more times, or two or more times. But since they can
still occur in any order, I'm not sure how to handle it. If I try:

language = expr1 & expr2 & Optional(expr3) & ZeroOrMore(expr4) &
ZeroOrMore(expr5)

Then parsing fails if all expr4's are not adjacent. My current idea is
to do the following:

multiples = ZeroOrMore(expr4 | expr5)

language = (multiples + expr1) & (multiples + expr2) &
Optional(multiples + expr3) & multiples

While its ugly, I can't think of any other way to do it. Additionally,
it doesn't get me any closer to implementing OneOrMore in an unsorted
set of expressions.

Re: [Pyparsing] Unordered set of expressions

[Paul M. <pt...@au...>]

Russell -

I'm not seeing this behavior:


from pyparsing import *

"""
language = expr1 & expr2 & Optional(expr3) & ZeroOrMore(expr4) &
ZeroOrMore(expr5)
"""

A = Literal("A")
B = Literal("B")
C = Literal("C")
D = Literal("D")
E = Literal("E")

lang = A & B & Optional(C) & ZeroOrMore(D) & ZeroOrMore(E)

tests = """\
    ABCDE
    ABDE
    AB
    BA
    EDCBA
    EAEB
    BEDCADEEDEDDEDD""".splitlines()

for t in tests:
    print t
    print lang.parseString(t, parseAll=True)
    print

prints:

    ABCDE
['A', 'B', 'C', 'D', 'E']

    ABDE
['A', 'B', 'D', 'E']

    AB
['A', 'B']

    BA
['B', 'A']

    EDCBA
['E', 'D', 'C', 'B', 'A']

    EAEB
['E', 'A', 'E', 'B']

    BEDCADEEDEDDEDD
['B', 'E', 'D', 'C', 'A', 'D', 'E', 'E', 'D', 'E', 'D', 'D', 'E', 'D', 'D']


All of my test cases parse successfully.  This is using the latest
pyparsing.

You can have as many D's and E's as you like, anywhere, and at most 1 C
anywhere, but you must have 1 A and 1 B, somewhere.

-- Paul


-----Original Message-----
From: Russell Dill [mailto:Rus...@as...] 
Sent: Thursday, September 29, 2011 1:25 PM
To: pyp...@li...
Subject: [Pyparsing] Unordered set of expressions

I have to parse something with an unordered set of expressions. In the
simplest case, some expressions are required, some are optional. For
this, parsing is easy:

language = expr1 & expr2 & Optional(expr3)

However, there are cases where an expression can occur zero or more
times, one or more times, or two or more times. But since they can
still occur in any order, I'm not sure how to handle it. If I try:

language = expr1 & expr2 & Optional(expr3) & ZeroOrMore(expr4) &
ZeroOrMore(expr5)

Then parsing fails if all expr4's are not adjacent. My current idea is
to do the following:

multiples = ZeroOrMore(expr4 | expr5)

language = (multiples + expr1) & (multiples + expr2) &
Optional(multiples + expr3) & multiples

While its ugly, I can't think of any other way to do it. Additionally,
it doesn't get me any closer to implementing OneOrMore in an unsorted
set of expressions.

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Re: [Pyparsing] Unordered set of expressions

[Russell D. <Rus...@as...>]

On Thu, Sep 29, 2011 at 4:09 PM, Paul McGuire <pt...@au...> wrote:
> Russell -
>
> I'm not seeing this behavior:
>
>    EAEB
> ['E', 'A', 'E', 'B']
>
> You can have as many D's and E's as you like, anywhere, and at most 1 C
> anywhere, but you must have 1 A and 1 B, somewhere.

Odd, at some point I must have convinced myself something about Each
that wasn't true. Ok, minor issue though, the Group keyword seems to
cause this to stop working. Since the order doesn't matter, it'd be
nice to Group them together. Naming them seems to be a workaround, but
it produces strange parse output.

ZeroOrMore(Literal("E")("Es")))


>
> -----Original Message-----
> From: Russell Dill [mailto:Rus...@as...]
> Sent: Thursday, September 29, 2011 1:25 PM
> To: pyp...@li...
> Subject: [Pyparsing] Unordered set of expressions
>
> I have to parse something with an unordered set of expressions. In the
> simplest case, some expressions are required, some are optional. For
> this, parsing is easy:
>
> language = expr1 & expr2 & Optional(expr3)
>
> However, there are cases where an expression can occur zero or more
> times, one or more times, or two or more times. But since they can
> still occur in any order, I'm not sure how to handle it. If I try:
>
> language = expr1 & expr2 & Optional(expr3) & ZeroOrMore(expr4) &
> ZeroOrMore(expr5)
>
> Then parsing fails if all expr4's are not adjacent. My current idea is
> to do the following:
>
> multiples = ZeroOrMore(expr4 | expr5)
>
> language = (multiples + expr1) & (multiples + expr2) &
> Optional(multiples + expr3) & multiples
>
> While its ugly, I can't think of any other way to do it. Additionally,
> it doesn't get me any closer to implementing OneOrMore in an unsorted
> set of expressions.
>
> ----------------------------------------------------------------------------
> --
> All the data continuously generated in your IT infrastructure contains a
> definitive record of customers, application performance, security
> threats, fraudulent activity and more. Splunk takes this data and makes
> sense of it. Business sense. IT sense. Common sense.
> http://p.sf.net/sfu/splunk-d2dcopy1
> _______________________________________________
> Pyparsing-users mailing list
> Pyp...@li...
> https://lists.sourceforge.net/lists/listinfo/pyparsing-users
>
>

Re: [Pyparsing] Unordered set of expressions

[Paul M. <pt...@au...>]

Russell -

Still not seeing the problem.


from pyparsing import *

"""
language = expr1 & expr2 & Optional(expr3) & ZeroOrMore(expr4) & ZeroOrMore(expr5)
"""

A = oneOf("A a")("As")
B = oneOf("B b")("Bs")
C = oneOf("C c")("Cs")
D = oneOf("D d")("Ds")
E = oneOf("E e")("Es")

lang = A & B & Optional(C) & ZeroOrMore(D) & ZeroOrMore(E)

tests = """\
    ABCDE
    ABDE
    AB
    BA
    EDCBA
    EaEB
    BeDCADEeDEDDeDD""".splitlines()

for t in tests:
    print t.strip()
    print lang.parseString(t, parseAll=True).dump()
    print


Prints:

ABCDE
['A', 'B', 'C', 'D', 'E']
- As: A
- Bs: B
- Cs: C
- Ds: D
- Es: E

ABDE
['A', 'B', 'D', 'E']
- As: A
- Bs: B
- Ds: D
- Es: E

AB
['A', 'B']
- As: A
- Bs: B

BA
['B', 'A']
- As: A
- Bs: B

EDCBA
['E', 'D', 'C', 'B', 'A']
- As: A
- Bs: B
- Cs: C
- Ds: D
- Es: E

EaEB
['E', 'a', 'E', 'B']
- As: a
- Bs: B
- Es: ['E', 'E']

BeDCADEeDEDDeDD
['B', 'e', 'D', 'C', 'A', 'D', 'E', 'e', 'D', 'E', 'D', 'D', 'e', 'D', 'D']
- As: A
- Bs: B
- Cs: C
- Ds: ['D', 'D', 'D', 'D', 'D', 'D', 'D']
- Es: ['e', 'E', 'e', 'E', 'e']


No Group required, and the parsed results look okay.

-- Paul

Re: [Pyparsing] Unordered set of expressions

[Russell D. <Rus...@as...>]

> No Group required, and the parsed results look okay.

Group() actually breaks it, so the naming is required instead. As for
the results, I was looking at the output without dump, my bad.

>>> lang = Word("A") & ZeroOrMore(Word("B")("Bs"))
>>> lang.parseString("B A B", parseAll=True)
(['B', 'A', 'B'], {'Bs': [('B', 0), ('B', 2), ((['B', 'B'], {}), 0)]})

Its correct.