split string at commas respecting quotes when string not in csv format

John Machin sjmachin at lexicon.net
Thu Mar 26 16:46:08 EDT 2009


On Mar 27, 6:51 am, "R. David Murray" <rdmur... at bitdance.com> wrote:
> OK, I've got a little problem that I'd like to ask the assembled minds
> for help with.  I can write code to parse this, but I'm thinking it may
> be possible to do it with regexes.  My regex foo isn't that good, so if
> anyone is willing to help (or offer an alternate parsing suggestion)
> I would be greatful.  (This has to be stdlib only, by the way, I
> can't introduce any new modules into the application so pyparsing is
> not an option.)
>
> The challenge is to turn a string like this:
>
>     a=1,b="0234,)#($)@", k="7"
>
> into this:
>
>     [("a", "1"), ("b", "0234,)#($)#"), ("k", "7")]

The challenge is for you to explain unambiguously what you want.

1. a=1 => "1" and k="7" => "7" ... is this a mistake or are the quotes
optional in the original string when not required to protect a comma?

2. What is the rule that explains the transmogrification of @ to # in
your example?

3. Is the input guaranteed to be syntactically correct?

The following should do close enough to what you want; adjust as
appropriate.

 >>> import re
 >>> s = """a=1,b="0234,)#($)@", k="7" """
 >>> rx = re.compile(r'[ ]*(\w+)=([^",]+|"[^"]*")[ ]*(?:,|$)')
 >>> rx.findall(s)
 [('a', '1'), ('b', '"0234,)#($)@"'), ('k', '"7"')]
 >>> rx.findall('a=1, *DODGY*SYNTAX* b=2')
 [('a', '1'), ('b', '2')]
 >>>

HTH,
John



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