Coverage for /pythoncovmergedfiles/medio/medio/usr/local/lib/python3.8/site-packages/lark/lark.py: 50%
329 statements
« prev ^ index » next coverage.py v7.3.1, created at 2023-09-25 06:30 +0000
1from abc import ABC, abstractmethod
2import getpass
3import sys, os, pickle
4import tempfile
5import types
6import re
7from typing import (
8 TypeVar, Type, List, Dict, Iterator, Callable, Union, Optional, Sequence,
9 Tuple, Iterable, IO, Any, TYPE_CHECKING, Collection
10)
11if TYPE_CHECKING:
12 from .parsers.lalr_interactive_parser import InteractiveParser
13 from .tree import ParseTree
14 from .visitors import Transformer
15 if sys.version_info >= (3, 8):
16 from typing import Literal
17 else:
18 from typing_extensions import Literal
19 from .parser_frontends import ParsingFrontend
21from .exceptions import ConfigurationError, assert_config, UnexpectedInput
22from .utils import Serialize, SerializeMemoizer, FS, isascii, logger
23from .load_grammar import load_grammar, FromPackageLoader, Grammar, verify_used_files, PackageResource, sha256_digest
24from .tree import Tree
25from .common import LexerConf, ParserConf, _ParserArgType, _LexerArgType
27from .lexer import Lexer, BasicLexer, TerminalDef, LexerThread, Token
28from .parse_tree_builder import ParseTreeBuilder
29from .parser_frontends import _validate_frontend_args, _get_lexer_callbacks, _deserialize_parsing_frontend, _construct_parsing_frontend
30from .grammar import Rule
33try:
34 import regex
35 _has_regex = True
36except ImportError:
37 _has_regex = False
40###{standalone
43class PostLex(ABC):
44 @abstractmethod
45 def process(self, stream: Iterator[Token]) -> Iterator[Token]:
46 return stream
48 always_accept: Iterable[str] = ()
50class LarkOptions(Serialize):
51 """Specifies the options for Lark
53 """
55 start: List[str]
56 debug: bool
57 strict: bool
58 transformer: 'Optional[Transformer]'
59 propagate_positions: Union[bool, str]
60 maybe_placeholders: bool
61 cache: Union[bool, str]
62 regex: bool
63 g_regex_flags: int
64 keep_all_tokens: bool
65 tree_class: Any
66 parser: _ParserArgType
67 lexer: _LexerArgType
68 ambiguity: 'Literal["auto", "resolve", "explicit", "forest"]'
69 postlex: Optional[PostLex]
70 priority: 'Optional[Literal["auto", "normal", "invert"]]'
71 lexer_callbacks: Dict[str, Callable[[Token], Token]]
72 use_bytes: bool
73 edit_terminals: Optional[Callable[[TerminalDef], TerminalDef]]
74 import_paths: 'List[Union[str, Callable[[Union[None, str, PackageResource], str], Tuple[str, str]]]]'
75 source_path: Optional[str]
77 OPTIONS_DOC = """
78 **=== General Options ===**
80 start
81 The start symbol. Either a string, or a list of strings for multiple possible starts (Default: "start")
82 debug
83 Display debug information and extra warnings. Use only when debugging (Default: ``False``)
84 When used with Earley, it generates a forest graph as "sppf.png", if 'dot' is installed.
85 strict
86 Throw an exception on any potential ambiguity, including shift/reduce conflicts, and regex collisions.
87 transformer
88 Applies the transformer to every parse tree (equivalent to applying it after the parse, but faster)
89 propagate_positions
90 Propagates positional attributes into the 'meta' attribute of all tree branches.
91 Sets attributes: (line, column, end_line, end_column, start_pos, end_pos,
92 container_line, container_column, container_end_line, container_end_column)
93 Accepts ``False``, ``True``, or a callable, which will filter which nodes to ignore when propagating.
94 maybe_placeholders
95 When ``True``, the ``[]`` operator returns ``None`` when not matched.
96 When ``False``, ``[]`` behaves like the ``?`` operator, and returns no value at all.
97 (default= ``True``)
98 cache
99 Cache the results of the Lark grammar analysis, for x2 to x3 faster loading. LALR only for now.
101 - When ``False``, does nothing (default)
102 - When ``True``, caches to a temporary file in the local directory
103 - When given a string, caches to the path pointed by the string
104 regex
105 When True, uses the ``regex`` module instead of the stdlib ``re``.
106 g_regex_flags
107 Flags that are applied to all terminals (both regex and strings)
108 keep_all_tokens
109 Prevent the tree builder from automagically removing "punctuation" tokens (Default: ``False``)
110 tree_class
111 Lark will produce trees comprised of instances of this class instead of the default ``lark.Tree``.
113 **=== Algorithm Options ===**
115 parser
116 Decides which parser engine to use. Accepts "earley" or "lalr". (Default: "earley").
117 (there is also a "cyk" option for legacy)
118 lexer
119 Decides whether or not to use a lexer stage
121 - "auto" (default): Choose for me based on the parser
122 - "basic": Use a basic lexer
123 - "contextual": Stronger lexer (only works with parser="lalr")
124 - "dynamic": Flexible and powerful (only with parser="earley")
125 - "dynamic_complete": Same as dynamic, but tries *every* variation of tokenizing possible.
126 ambiguity
127 Decides how to handle ambiguity in the parse. Only relevant if parser="earley"
129 - "resolve": The parser will automatically choose the simplest derivation
130 (it chooses consistently: greedy for tokens, non-greedy for rules)
131 - "explicit": The parser will return all derivations wrapped in "_ambig" tree nodes (i.e. a forest).
132 - "forest": The parser will return the root of the shared packed parse forest.
134 **=== Misc. / Domain Specific Options ===**
136 postlex
137 Lexer post-processing (Default: ``None``) Only works with the basic and contextual lexers.
138 priority
139 How priorities should be evaluated - "auto", ``None``, "normal", "invert" (Default: "auto")
140 lexer_callbacks
141 Dictionary of callbacks for the lexer. May alter tokens during lexing. Use with caution.
142 use_bytes
143 Accept an input of type ``bytes`` instead of ``str``.
144 edit_terminals
145 A callback for editing the terminals before parse.
146 import_paths
147 A List of either paths or loader functions to specify from where grammars are imported
148 source_path
149 Override the source of from where the grammar was loaded. Useful for relative imports and unconventional grammar loading
150 **=== End of Options ===**
151 """
152 if __doc__:
153 __doc__ += OPTIONS_DOC
156 # Adding a new option needs to be done in multiple places:
157 # - In the dictionary below. This is the primary truth of which options `Lark.__init__` accepts
158 # - In the docstring above. It is used both for the docstring of `LarkOptions` and `Lark`, and in readthedocs
159 # - As an attribute of `LarkOptions` above
160 # - Potentially in `_LOAD_ALLOWED_OPTIONS` below this class, when the option doesn't change how the grammar is loaded
161 # - Potentially in `lark.tools.__init__`, if it makes sense, and it can easily be passed as a cmd argument
162 _defaults: Dict[str, Any] = {
163 'debug': False,
164 'strict': False,
165 'keep_all_tokens': False,
166 'tree_class': None,
167 'cache': False,
168 'postlex': None,
169 'parser': 'earley',
170 'lexer': 'auto',
171 'transformer': None,
172 'start': 'start',
173 'priority': 'auto',
174 'ambiguity': 'auto',
175 'regex': False,
176 'propagate_positions': False,
177 'lexer_callbacks': {},
178 'maybe_placeholders': True,
179 'edit_terminals': None,
180 'g_regex_flags': 0,
181 'use_bytes': False,
182 'import_paths': [],
183 'source_path': None,
184 '_plugins': {},
185 }
187 def __init__(self, options_dict: Dict[str, Any]) -> None:
188 o = dict(options_dict)
190 options = {}
191 for name, default in self._defaults.items():
192 if name in o:
193 value = o.pop(name)
194 if isinstance(default, bool) and name not in ('cache', 'use_bytes', 'propagate_positions'):
195 value = bool(value)
196 else:
197 value = default
199 options[name] = value
201 if isinstance(options['start'], str):
202 options['start'] = [options['start']]
204 self.__dict__['options'] = options
207 assert_config(self.parser, ('earley', 'lalr', 'cyk', None))
209 if self.parser == 'earley' and self.transformer:
210 raise ConfigurationError('Cannot specify an embedded transformer when using the Earley algorithm. '
211 'Please use your transformer on the resulting parse tree, or use a different algorithm (i.e. LALR)')
213 if o:
214 raise ConfigurationError("Unknown options: %s" % o.keys())
216 def __getattr__(self, name: str) -> Any:
217 try:
218 return self.__dict__['options'][name]
219 except KeyError as e:
220 raise AttributeError(e)
222 def __setattr__(self, name: str, value: str) -> None:
223 assert_config(name, self.options.keys(), "%r isn't a valid option. Expected one of: %s")
224 self.options[name] = value
226 def serialize(self, memo = None) -> Dict[str, Any]:
227 return self.options
229 @classmethod
230 def deserialize(cls, data: Dict[str, Any], memo: Dict[int, Union[TerminalDef, Rule]]) -> "LarkOptions":
231 return cls(data)
234# Options that can be passed to the Lark parser, even when it was loaded from cache/standalone.
235# These options are only used outside of `load_grammar`.
236_LOAD_ALLOWED_OPTIONS = {'postlex', 'transformer', 'lexer_callbacks', 'use_bytes', 'debug', 'g_regex_flags', 'regex', 'propagate_positions', 'tree_class', '_plugins'}
238_VALID_PRIORITY_OPTIONS = ('auto', 'normal', 'invert', None)
239_VALID_AMBIGUITY_OPTIONS = ('auto', 'resolve', 'explicit', 'forest')
242_T = TypeVar('_T', bound="Lark")
244class Lark(Serialize):
245 """Main interface for the library.
247 It's mostly a thin wrapper for the many different parsers, and for the tree constructor.
249 Parameters:
250 grammar: a string or file-object containing the grammar spec (using Lark's ebnf syntax)
251 options: a dictionary controlling various aspects of Lark.
253 Example:
254 >>> Lark(r'''start: "foo" ''')
255 Lark(...)
256 """
258 source_path: str
259 source_grammar: str
260 grammar: 'Grammar'
261 options: LarkOptions
262 lexer: Lexer
263 parser: 'ParsingFrontend'
264 terminals: Collection[TerminalDef]
266 def __init__(self, grammar: 'Union[Grammar, str, IO[str]]', **options) -> None:
267 self.options = LarkOptions(options)
268 re_module: types.ModuleType
270 # Set regex or re module
271 use_regex = self.options.regex
272 if use_regex:
273 if _has_regex:
274 re_module = regex
275 else:
276 raise ImportError('`regex` module must be installed if calling `Lark(regex=True)`.')
277 else:
278 re_module = re
280 # Some, but not all file-like objects have a 'name' attribute
281 if self.options.source_path is None:
282 try:
283 self.source_path = grammar.name # type: ignore[union-attr]
284 except AttributeError:
285 self.source_path = '<string>'
286 else:
287 self.source_path = self.options.source_path
289 # Drain file-like objects to get their contents
290 try:
291 read = grammar.read # type: ignore[union-attr]
292 except AttributeError:
293 pass
294 else:
295 grammar = read()
297 cache_fn = None
298 cache_sha256 = None
299 if isinstance(grammar, str):
300 self.source_grammar = grammar
301 if self.options.use_bytes:
302 if not isascii(grammar):
303 raise ConfigurationError("Grammar must be ascii only, when use_bytes=True")
305 if self.options.cache:
306 if self.options.parser != 'lalr':
307 raise ConfigurationError("cache only works with parser='lalr' for now")
309 unhashable = ('transformer', 'postlex', 'lexer_callbacks', 'edit_terminals', '_plugins')
310 options_str = ''.join(k+str(v) for k, v in options.items() if k not in unhashable)
311 from . import __version__
312 s = grammar + options_str + __version__ + str(sys.version_info[:2])
313 cache_sha256 = sha256_digest(s)
315 if isinstance(self.options.cache, str):
316 cache_fn = self.options.cache
317 else:
318 if self.options.cache is not True:
319 raise ConfigurationError("cache argument must be bool or str")
321 try:
322 username = getpass.getuser()
323 except Exception:
324 # The exception raised may be ImportError or OSError in
325 # the future. For the cache, we don't care about the
326 # specific reason - we just want a username.
327 username = "unknown"
329 cache_fn = tempfile.gettempdir() + "/.lark_cache_%s_%s_%s_%s.tmp" % (username, cache_sha256, *sys.version_info[:2])
331 old_options = self.options
332 try:
333 with FS.open(cache_fn, 'rb') as f:
334 logger.debug('Loading grammar from cache: %s', cache_fn)
335 # Remove options that aren't relevant for loading from cache
336 for name in (set(options) - _LOAD_ALLOWED_OPTIONS):
337 del options[name]
338 file_sha256 = f.readline().rstrip(b'\n')
339 cached_used_files = pickle.load(f)
340 if file_sha256 == cache_sha256.encode('utf8') and verify_used_files(cached_used_files):
341 cached_parser_data = pickle.load(f)
342 self._load(cached_parser_data, **options)
343 return
344 except FileNotFoundError:
345 # The cache file doesn't exist; parse and compose the grammar as normal
346 pass
347 except Exception: # We should probably narrow done which errors we catch here.
348 logger.exception("Failed to load Lark from cache: %r. We will try to carry on.", cache_fn)
350 # In theory, the Lark instance might have been messed up by the call to `_load`.
351 # In practice the only relevant thing that might have been overwritten should be `options`
352 self.options = old_options
355 # Parse the grammar file and compose the grammars
356 self.grammar, used_files = load_grammar(grammar, self.source_path, self.options.import_paths, self.options.keep_all_tokens)
357 else:
358 assert isinstance(grammar, Grammar)
359 self.grammar = grammar
362 if self.options.lexer == 'auto':
363 if self.options.parser == 'lalr':
364 self.options.lexer = 'contextual'
365 elif self.options.parser == 'earley':
366 if self.options.postlex is not None:
367 logger.info("postlex can't be used with the dynamic lexer, so we use 'basic' instead. "
368 "Consider using lalr with contextual instead of earley")
369 self.options.lexer = 'basic'
370 else:
371 self.options.lexer = 'dynamic'
372 elif self.options.parser == 'cyk':
373 self.options.lexer = 'basic'
374 else:
375 assert False, self.options.parser
376 lexer = self.options.lexer
377 if isinstance(lexer, type):
378 assert issubclass(lexer, Lexer) # XXX Is this really important? Maybe just ensure interface compliance
379 else:
380 assert_config(lexer, ('basic', 'contextual', 'dynamic', 'dynamic_complete'))
381 if self.options.postlex is not None and 'dynamic' in lexer:
382 raise ConfigurationError("Can't use postlex with a dynamic lexer. Use basic or contextual instead")
384 if self.options.ambiguity == 'auto':
385 if self.options.parser == 'earley':
386 self.options.ambiguity = 'resolve'
387 else:
388 assert_config(self.options.parser, ('earley', 'cyk'), "%r doesn't support disambiguation. Use one of these parsers instead: %s")
390 if self.options.priority == 'auto':
391 self.options.priority = 'normal'
393 if self.options.priority not in _VALID_PRIORITY_OPTIONS:
394 raise ConfigurationError("invalid priority option: %r. Must be one of %r" % (self.options.priority, _VALID_PRIORITY_OPTIONS))
395 if self.options.ambiguity not in _VALID_AMBIGUITY_OPTIONS:
396 raise ConfigurationError("invalid ambiguity option: %r. Must be one of %r" % (self.options.ambiguity, _VALID_AMBIGUITY_OPTIONS))
398 if self.options.parser is None:
399 terminals_to_keep = '*'
400 elif self.options.postlex is not None:
401 terminals_to_keep = set(self.options.postlex.always_accept)
402 else:
403 terminals_to_keep = set()
405 # Compile the EBNF grammar into BNF
406 self.terminals, self.rules, self.ignore_tokens = self.grammar.compile(self.options.start, terminals_to_keep)
408 if self.options.edit_terminals:
409 for t in self.terminals:
410 self.options.edit_terminals(t)
412 self._terminals_dict = {t.name: t for t in self.terminals}
414 # If the user asked to invert the priorities, negate them all here.
415 if self.options.priority == 'invert':
416 for rule in self.rules:
417 if rule.options.priority is not None:
418 rule.options.priority = -rule.options.priority
419 for term in self.terminals:
420 term.priority = -term.priority
421 # Else, if the user asked to disable priorities, strip them from the
422 # rules and terminals. This allows the Earley parsers to skip an extra forest walk
423 # for improved performance, if you don't need them (or didn't specify any).
424 elif self.options.priority is None:
425 for rule in self.rules:
426 if rule.options.priority is not None:
427 rule.options.priority = None
428 for term in self.terminals:
429 term.priority = 0
431 # TODO Deprecate lexer_callbacks?
432 self.lexer_conf = LexerConf(
433 self.terminals, re_module, self.ignore_tokens, self.options.postlex,
434 self.options.lexer_callbacks, self.options.g_regex_flags, use_bytes=self.options.use_bytes, strict=self.options.strict
435 )
437 if self.options.parser:
438 self.parser = self._build_parser()
439 elif lexer:
440 self.lexer = self._build_lexer()
442 if cache_fn:
443 logger.debug('Saving grammar to cache: %s', cache_fn)
444 try:
445 with FS.open(cache_fn, 'wb') as f:
446 assert cache_sha256 is not None
447 f.write(cache_sha256.encode('utf8') + b'\n')
448 pickle.dump(used_files, f)
449 self.save(f, _LOAD_ALLOWED_OPTIONS)
450 except IOError as e:
451 logger.exception("Failed to save Lark to cache: %r.", cache_fn, e)
453 if __doc__:
454 __doc__ += "\n\n" + LarkOptions.OPTIONS_DOC
456 __serialize_fields__ = 'parser', 'rules', 'options'
458 def _build_lexer(self, dont_ignore: bool=False) -> BasicLexer:
459 lexer_conf = self.lexer_conf
460 if dont_ignore:
461 from copy import copy
462 lexer_conf = copy(lexer_conf)
463 lexer_conf.ignore = ()
464 return BasicLexer(lexer_conf)
466 def _prepare_callbacks(self) -> None:
467 self._callbacks = {}
468 # we don't need these callbacks if we aren't building a tree
469 if self.options.ambiguity != 'forest':
470 self._parse_tree_builder = ParseTreeBuilder(
471 self.rules,
472 self.options.tree_class or Tree,
473 self.options.propagate_positions,
474 self.options.parser != 'lalr' and self.options.ambiguity == 'explicit',
475 self.options.maybe_placeholders
476 )
477 self._callbacks = self._parse_tree_builder.create_callback(self.options.transformer)
478 self._callbacks.update(_get_lexer_callbacks(self.options.transformer, self.terminals))
480 def _build_parser(self) -> "ParsingFrontend":
481 self._prepare_callbacks()
482 _validate_frontend_args(self.options.parser, self.options.lexer)
483 parser_conf = ParserConf(self.rules, self._callbacks, self.options.start)
484 return _construct_parsing_frontend(
485 self.options.parser,
486 self.options.lexer,
487 self.lexer_conf,
488 parser_conf,
489 options=self.options
490 )
492 def save(self, f, exclude_options: Collection[str] = ()) -> None:
493 """Saves the instance into the given file object
495 Useful for caching and multiprocessing.
496 """
497 if self.options.parser != 'lalr':
498 raise NotImplementedError("Lark.save() is only implemented for the LALR(1) parser.")
499 data, m = self.memo_serialize([TerminalDef, Rule])
500 if exclude_options:
501 data["options"] = {n: v for n, v in data["options"].items() if n not in exclude_options}
502 pickle.dump({'data': data, 'memo': m}, f, protocol=pickle.HIGHEST_PROTOCOL)
504 @classmethod
505 def load(cls: Type[_T], f) -> _T:
506 """Loads an instance from the given file object
508 Useful for caching and multiprocessing.
509 """
510 inst = cls.__new__(cls)
511 return inst._load(f)
513 def _deserialize_lexer_conf(self, data: Dict[str, Any], memo: Dict[int, Union[TerminalDef, Rule]], options: LarkOptions) -> LexerConf:
514 lexer_conf = LexerConf.deserialize(data['lexer_conf'], memo)
515 lexer_conf.callbacks = options.lexer_callbacks or {}
516 lexer_conf.re_module = regex if options.regex else re
517 lexer_conf.use_bytes = options.use_bytes
518 lexer_conf.g_regex_flags = options.g_regex_flags
519 lexer_conf.skip_validation = True
520 lexer_conf.postlex = options.postlex
521 return lexer_conf
523 def _load(self: _T, f: Any, **kwargs) -> _T:
524 if isinstance(f, dict):
525 d = f
526 else:
527 d = pickle.load(f)
528 memo_json = d['memo']
529 data = d['data']
531 assert memo_json
532 memo = SerializeMemoizer.deserialize(memo_json, {'Rule': Rule, 'TerminalDef': TerminalDef}, {})
533 options = dict(data['options'])
534 if (set(kwargs) - _LOAD_ALLOWED_OPTIONS) & set(LarkOptions._defaults):
535 raise ConfigurationError("Some options are not allowed when loading a Parser: {}"
536 .format(set(kwargs) - _LOAD_ALLOWED_OPTIONS))
537 options.update(kwargs)
538 self.options = LarkOptions.deserialize(options, memo)
539 self.rules = [Rule.deserialize(r, memo) for r in data['rules']]
540 self.source_path = '<deserialized>'
541 _validate_frontend_args(self.options.parser, self.options.lexer)
542 self.lexer_conf = self._deserialize_lexer_conf(data['parser'], memo, self.options)
543 self.terminals = self.lexer_conf.terminals
544 self._prepare_callbacks()
545 self._terminals_dict = {t.name: t for t in self.terminals}
546 self.parser = _deserialize_parsing_frontend(
547 data['parser'],
548 memo,
549 self.lexer_conf,
550 self._callbacks,
551 self.options, # Not all, but multiple attributes are used
552 )
553 return self
555 @classmethod
556 def _load_from_dict(cls, data, memo, **kwargs):
557 inst = cls.__new__(cls)
558 return inst._load({'data': data, 'memo': memo}, **kwargs)
560 @classmethod
561 def open(cls: Type[_T], grammar_filename: str, rel_to: Optional[str]=None, **options) -> _T:
562 """Create an instance of Lark with the grammar given by its filename
564 If ``rel_to`` is provided, the function will find the grammar filename in relation to it.
566 Example:
568 >>> Lark.open("grammar_file.lark", rel_to=__file__, parser="lalr")
569 Lark(...)
571 """
572 if rel_to:
573 basepath = os.path.dirname(rel_to)
574 grammar_filename = os.path.join(basepath, grammar_filename)
575 with open(grammar_filename, encoding='utf8') as f:
576 return cls(f, **options)
578 @classmethod
579 def open_from_package(cls: Type[_T], package: str, grammar_path: str, search_paths: 'Sequence[str]'=[""], **options) -> _T:
580 """Create an instance of Lark with the grammar loaded from within the package `package`.
581 This allows grammar loading from zipapps.
583 Imports in the grammar will use the `package` and `search_paths` provided, through `FromPackageLoader`
585 Example:
587 Lark.open_from_package(__name__, "example.lark", ("grammars",), parser=...)
588 """
589 package_loader = FromPackageLoader(package, search_paths)
590 full_path, text = package_loader(None, grammar_path)
591 options.setdefault('source_path', full_path)
592 options.setdefault('import_paths', [])
593 options['import_paths'].append(package_loader)
594 return cls(text, **options)
596 def __repr__(self):
597 return 'Lark(open(%r), parser=%r, lexer=%r, ...)' % (self.source_path, self.options.parser, self.options.lexer)
600 def lex(self, text: str, dont_ignore: bool=False) -> Iterator[Token]:
601 """Only lex (and postlex) the text, without parsing it. Only relevant when lexer='basic'
603 When dont_ignore=True, the lexer will return all tokens, even those marked for %ignore.
605 :raises UnexpectedCharacters: In case the lexer cannot find a suitable match.
606 """
607 lexer: Lexer
608 if not hasattr(self, 'lexer') or dont_ignore:
609 lexer = self._build_lexer(dont_ignore)
610 else:
611 lexer = self.lexer
612 lexer_thread = LexerThread.from_text(lexer, text)
613 stream = lexer_thread.lex(None)
614 if self.options.postlex:
615 return self.options.postlex.process(stream)
616 return stream
618 def get_terminal(self, name: str) -> TerminalDef:
619 """Get information about a terminal"""
620 return self._terminals_dict[name]
622 def parse_interactive(self, text: Optional[str]=None, start: Optional[str]=None) -> 'InteractiveParser':
623 """Start an interactive parsing session.
625 Parameters:
626 text (str, optional): Text to be parsed. Required for ``resume_parse()``.
627 start (str, optional): Start symbol
629 Returns:
630 A new InteractiveParser instance.
632 See Also: ``Lark.parse()``
633 """
634 return self.parser.parse_interactive(text, start=start)
636 def parse(self, text: str, start: Optional[str]=None, on_error: 'Optional[Callable[[UnexpectedInput], bool]]'=None) -> 'ParseTree':
637 """Parse the given text, according to the options provided.
639 Parameters:
640 text (str): Text to be parsed.
641 start (str, optional): Required if Lark was given multiple possible start symbols (using the start option).
642 on_error (function, optional): if provided, will be called on UnexpectedToken error. Return true to resume parsing.
643 LALR only. See examples/advanced/error_handling.py for an example of how to use on_error.
645 Returns:
646 If a transformer is supplied to ``__init__``, returns whatever is the
647 result of the transformation. Otherwise, returns a Tree instance.
649 :raises UnexpectedInput: On a parse error, one of these sub-exceptions will rise:
650 ``UnexpectedCharacters``, ``UnexpectedToken``, or ``UnexpectedEOF``.
651 For convenience, these sub-exceptions also inherit from ``ParserError`` and ``LexerError``.
653 """
654 return self.parser.parse(text, start=start, on_error=on_error)
657###}