python - Pyparsing: Parse nested, typed parameter list with nestedExpr -


i have typed , optionally nested parameter list parse.

input: (int:1, float:3, list:(float:4, int:5))  expected dump: [[['int', '1'], ['float', '3'], ['list', [['float', '4'], ['int', '5']]]]]

if type omitted, depending of following value standard type should chosen:

input: (1, float:3, (4, int:5))  expected dump: [[['str', '1'], ['float', '3'], ['tuple', [['str', '4'], ['int', '5']]]]]

as might expect use types in parseaction transform values automatically during parsing. step works, hence skip here.

my approach of problem is:

import pyparsing pp  dicasttypes={     "str": lambda value: value,     "int": lambda value: int(value),     "float": lambda value: float(value),      "tuple": lambda value: tuple(value),     "list": lambda value: list(value),     "set": lambda value: set(value),     "dict": lambda value: dict(value), }  bsquoted = lambda expr : pp.literal('\\').suppress() + expr  def parsingstring (specialsigns = '', printables = pp.printables):     sespecialsigns = set(specialsigns).union(set('\\'))     signs = ''.join(sorted(set(printables).difference(sespecialsigns)))     allowedliterals = (         pp.literal(r"\t").setparseaction(lambda : "\t")      |         pp.literal(r"\ ").setparseaction(lambda : " ")       |          pp.literal(r"\n").setparseaction(lambda : "\n")      |          pp.word(signs)                                       |         bsquoted('"')                                        |          bsquoted("'")     )     special in sespecialsigns:         allowedliterals = allowedliterals | bsquoted(special)                return pp.combine(pp.oneormore(allowedliterals))  value = parsingstring('(),=:') nestedvalue = pp.forward() castpattern = pp.optional(pp.oneof(list(dicasttypes.keys())) + pp.literal(":").suppress(), "str")("casttype") castpatternseq = pp.optional(pp.oneof(list(dicasttypes.keys())) + pp.literal(":").suppress(), "tuple")("casttype") parametervalue = pp.nestedexpr(content=(     pp.group(          (castpattern + value("rawvalue")) |          (castpatternseq + nestedvalue)     ) |      pp.literal(',').suppress() )) nestedvalue <<= parametervalue

this implementation works correctly, have serious problem default values of nested sequences:

parametervalue.parsestring('(int:1, float:3, list:(float:4, int:5))').dump() "[[['int', '1'], ['float', '3'], ['list', [['float', '4'], ['int', '5']]]]]"  parametervalue.parsestring('(1, float:3, (4, int:5))').dump() "[[['str', '1'], ['float', '3'], [['str', '4'], ['int', '5']]]]"

as can see, expected default value tuple sequence not set , depth of result list not correct. guess nestedexpr() catches pattern (4, int:5) before comes through parser (castpatternseq + nestedvalue). problem serious me, because plan call parseraction inside the nestedexpr pattern:

(castpattern + value("rawvalue")).setparseaction(castparameter)) |  (castpatternseq + nestedvalue).setparseaction(castparameter))

this works well, if type given explicitly, of course fails otherwise.

is there opportunity make nestedexpr little bit less greedy?

update 1

hi guys. after wasting whole day yesterday, instantly found solution problem described above morning.

i added delimitedlist implementation:

value = parsingstring('(),=:') nestedvalue = pp.forward() castpattern = pp.optional(pp.oneof(list(dicasttypes.keys())) + pp.literal(":").suppress(), "str")("casttype") castpatternseq = pp.optional(pp.oneof(list(dicasttypes.keys())) + pp.literal(":").suppress(), "tuple")("casttype") parametervalue = pp.nestedexpr(content=pp.delimitedlist(     pp.group(          (castpattern + value("rawvalue")) |          (castpatternseq + nestedvalue)     ) )) nestedvalue <<= parametervalue

this works well, not pretty well, can see in following examples:

parametervalue.parsestring('(int:1, (int:2, int:4))').dump() "[[['int', '1'], ['tuple', [['int', '2'], ['int', '4']]]]]"  parametervalue.parsestring('(int:1, ((int:2, int:4), (int:6, int9)) )').dump() pyparsing.parseexception: expected ")" (at char 6), (line:1, col:7)  parametervalue.parsestring('(int:1, ((int:2, int:4) (int:6, int:9)) )').dump() "[[['int', '1'], ['tuple', [[['int', '2'], ['int', '4']], [['int', '6'], ['int', '9']]]]]]"  parametervalue.parsestring('(int:1, (tuple:(int:2, int:4) tuple:(int:6, int9)) )').dump() "[[['int', '1'], ['tuple', [['tuple', [['int', '2'], ['int', '4']]], ['tuple', [['int', '6'], ['str', 'int9']]]]]]]"

the exception in example 2 lets me think, nestedexpr , delimitedlist don't work each other, they're catching pattern each other. ever reason might be, seems on problem, because if omit , in example 3, delimitedlist has nothing catch , whole pattern matches. not expected, because default types missing again. without , , explicit types parsing works well.

any ideas?

update 2

the problem, statement 

parametervalue.parsestring('(int:1, ((int:2, int:4), (int:6, int9)) )').dump()

raises exception, can solved altering implementation little bit (but seems more hack solution). i've added expression | pp.literal(",").suppress():

value = parsingstring('(),=:') nestedvalue = pp.forward() castpattern = pp.optional(pp.oneof(list(dicasttypes.keys())) + pp.literal(":").suppress(), "str")("casttype") castpatternseq = pp.optional(pp.oneof(list(dicasttypes.keys())) + pp.literal(":").suppress(), "tuple")("casttype") parametervalue = pp.nestedexpr(content=pp.delimitedlist(     pp.group(          (castpattern + value("rawvalue")) |          (castpatternseq + nestedvalue)     ) ) | pp.literal(",").suppress()) nestedvalue <<= parametervalue


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