Question

我有一个由“语句”列表组成的文件，每个语句都包含一个以逗号分隔的可变长度“列”列表，其中语句的结尾用分号表示：

head(
    col1,
    col2
);
head2(
    col1,
    col2,
    col3
);

我有一个完整文件的工作语法，但是如果其中一个列中存在语法错误，则错误消息的信息量不大 - 它基本上表示整个语句在开头语中都不好。

所以我想分别解析每一列，以便更有信息地报告该列中的错误。以下内容将解析整个文件（两个语句）并从解析操作中打印每个语句和列列表：

from pyparsing import Group, Literal, ParseException
from pyparsing import SkipTo, Suppress, commaSeparatedList
from pyparsing import Word, ZeroOrMore, alphas, alphanums

def parse_stmt(strng, loc, toks):
    print("++",toks,"++",loc,"++")

def parse_col(strng, loc, toks):
    # cols = commaSeparatedList(toks)
    print("==",toks,"===",loc,"==")

specs = '$_-'
name = Word(alphas+specs, alphanums+specs)
term = Literal(')') + Literal(';')
init = name
statement = Group(init.setParseAction(parse_stmt) + Suppress(Literal('(')) + \
            SkipTo(term).setParseAction(parse_col) + Suppress(term))
script = ZeroOrMore(statement)

ss = '\
abc(d 45, e, f g h); \
s2("much" "stuff", 34 48); \
'

print(ss)
try:
    print(script.parseString(ss))
except ParseException as err:
    print(" "*(err.column-1) + "^")
    print(err)

导致：

abc(d 45, e, f g h); s2("much" "stuff", 34 48); 
++ ['abc'] ++ 0 ++
== ['d 45, e, f g h'] === 4 ==
++ ['s2'] ++ 21 ++
== ['"much" "stuff", 34 48'] === 24 ==
[['abc', 'd 45, e, f g h'], ['s2', '"much" "stuff", 34 48']]

但是一旦我尝试通过取消注释cols = commaSeparatedList(toks)来解析列列表，一切都会爆炸：

abc(d 45, e, f g h); s2("much" "stuff", 34 48); 
++ ['abc'] ++ 0 ++
Traceback (most recent call last):
  File "pt.py", line 27, in <module>
    print(script.parseString(ss))
  File "pyparsing.py", line 1115, in parseString
    loc, tokens = self._parse( instring, 0 )
  File "pyparsing.py", line 989, in _parseNoCache
    loc,tokens = self.parseImpl( instring, preloc, doActions )
  File "pyparsing.py", line 2732, in parseImpl
    loc, tokens = self.expr._parse( instring, loc, doActions, callPreParse=False )
  File "pyparsing.py", line 989, in _parseNoCache
    loc,tokens = self.parseImpl( instring, preloc, doActions )
  File "pyparsing.py", line 2624, in parseImpl
    return self.expr._parse( instring, loc, doActions, callPreParse=False )
  File "pyparsing.py", line 989, in _parseNoCache
    loc,tokens = self.parseImpl( instring, preloc, doActions )
  File "pyparsing.py", line 2378, in parseImpl
    loc, exprtokens = e._parse( instring, loc, doActions )
  File "pyparsing.py", line 1015, in _parseNoCache
    tokens = fn( instring, tokensStart, retTokens )
  File "pyparsing.py", line 779, in wrapper
    ret = func(*args[limit[0]:])
TypeError: parse_col() missing 3 required positional arguments: 'strng', 'loc', and 'toks'

我的问题不涉及多线程或递归，但它似乎表明了对可能与context in pyparsing parse actions besides globals有关的可重入调用pyparsing的问题。

是否有一种简单的方法可以从一个动作中调用pyparsing例程，这个方法比该问题的答案更简单？

Answer 1

更改

cols = commaSeparatedList(toks)

到

cols = commaSeparatedList.parseString(toks[0])

似乎几乎可以修复它，至少对于您提供的数据示例。但是＆＃34;很多＆＃34; ＆＃34;东西＆＃34;似乎打破了csl解析器，可能是因为它希望在关闭后使用逗号＃34; ＆＃34;很多＆＃34;。

Pyparsing - 从解析操作中解析子语法

1 个答案: