"Benjamin Georgi" <[EMAIL PROTECTED]> wrote in message
news:[EMAIL PROTECTED]
> Hello list,
>
> I could use some help extracting the keys/values of a list of dictionaries
> from a string that is just the str() representation of the list (the
> problem is related to some flat file format I'm using for file IO).
>
> Example:
> >>> s = str(dict_list)
> >>> s
> '[{0: [2], 1: []}, {0: [], 1: [], 2: []}, {0: [1, 2]}]'
>
Pyparsing comes with a working example that will parse strings representing
lists, even if they are nested. This is actually more complex than the
example you've given - none of your lists is nested. Here is that example,
adapted to handle dict elements, too.
-- Paul
(The pyparsing home page/wiki is at pyparsing.wikispaces.com.)
from pyparsing import *
cvtInt = lambda toks: int(toks[0])
cvtReal = lambda toks: float(toks[0])
cvtTuple = lambda toks : tuple(toks.asList())
cvtDict = lambda toks: dict(toks.asList())
# define punctuation as suppressed literals
lparen,rparen,lbrack,rbrack,lbrace,rbrace,colon = \
map(Suppress,"()[]{}:")
integer = Combine(Optional(oneOf("+ -")) + Word(nums))\
.setName("integer")\
.setParseAction( cvtInt )
real = Combine(Optional(oneOf("+ -")) + Word(nums) + "." +
Optional(Word(nums)))\
.setName("real")\
.setParseAction( cvtReal )
tupleStr = Forward()
listStr = Forward()
dictStr = Forward()
listItem = real|integer|quotedString.setParseAction(removeQuotes)| \
Group(listStr) | tupleStr | dictStr
tupleStr << ( Suppress("(") + Optional(delimitedList(listItem)) +
Optional(Suppress(",")) + Suppress(")") )
tupleStr.setParseAction( cvtTuple )
listStr << (lbrack + Optional(delimitedList(listItem) +
Optional(Suppress(","))) + rbrack)
dictEntry = Group( listItem + colon + listItem )
dictStr << (lbrace + Optional(delimitedList(dictEntry) + \
Optional(Suppress(","))) + rbrace)
dictStr.setParseAction( cvtDict )
tests = """['a', 100, ('A', [101,102]), 3.14, [ +2.718, 'xyzzy', -1.414] ]
[{0: [2], 1: []}, {0: [], 1: [], 2: []}, {0: [1, 2]}]"""
for test in tests.split("\n"):
print "Test:", test.strip()
result = listStr.parseString(test)
print "Result:", result
for dd in result:
if isinstance(dd,dict): print dd.items()
print
Prints:
Test: ['a', 100, ('A', [101,102]), 3.14, [ +2.718, 'xyzzy', -1.414] ]
Result: ['a', 100, ('A', [101, 102]), 3.1400000000000001, [2.718,
'xyzzy', -1.4139999999999999]]
Test: [{0: [2], 1: []}, {0: [], 1: [], 2: []}, {0: [1, 2]}]
Result: [{0: [2], 1: []}, {0: [], 1: [], 2: []}, {0: [1, 2]}]
[(0, [2]), (1, [])]
[(0, []), (1, []), (2, [])]
[(0, [1, 2])]
--
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