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264 lines
7.8 KiB
Python
264 lines
7.8 KiB
Python
# actions.py
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from __future__ import annotations
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from typing import Union, Callable, Any
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from .exceptions import ParseException
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from .util import col, replaced_by_pep8
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from .results import ParseResults
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ParseAction = Union[
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Callable[[], Any],
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Callable[[ParseResults], Any],
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Callable[[int, ParseResults], Any],
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Callable[[str, int, ParseResults], Any],
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]
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class OnlyOnce:
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"""
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Wrapper for parse actions, to ensure they are only called once.
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Note: parse action signature must include all 3 arguments.
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"""
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def __init__(self, method_call: Callable[[str, int, ParseResults], Any]) -> None:
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from .core import _trim_arity
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self.callable = _trim_arity(method_call)
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self.called = False
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def __call__(self, s: str, l: int, t: ParseResults) -> ParseResults:
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if not self.called:
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results = self.callable(s, l, t)
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self.called = True
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return results
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raise ParseException(s, l, "OnlyOnce obj called multiple times w/out reset")
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def reset(self):
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"""
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Allow the associated parse action to be called once more.
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"""
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self.called = False
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def match_only_at_col(n: int) -> ParseAction:
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"""
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Helper method for defining parse actions that require matching at
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a specific column in the input text.
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"""
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def verify_col(strg: str, locn: int, toks: ParseResults) -> None:
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if col(locn, strg) != n:
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raise ParseException(strg, locn, f"matched token not at column {n}")
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return verify_col
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def replace_with(repl_str: Any) -> ParseAction:
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"""
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Helper method for common parse actions that simply return
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a literal value. Especially useful when used with
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:meth:`~ParserElement.transform_string`.
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Example:
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.. doctest::
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>>> num = Word(nums).set_parse_action(lambda toks: int(toks[0]))
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>>> na = one_of("N/A NA").set_parse_action(replace_with(math.nan))
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>>> term = na | num
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>>> term[1, ...].parse_string("324 234 N/A 234")
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ParseResults([324, 234, nan, 234], {})
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"""
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return lambda s, l, t: [repl_str]
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def remove_quotes(s: str, l: int, t: ParseResults) -> Any:
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r"""
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Helper parse action for removing quotation marks from parsed
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quoted strings, that use a single character for quoting. For parsing
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strings that may have multiple characters, use the :class:`QuotedString`
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class.
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Example:
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.. doctest::
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>>> # by default, quotation marks are included in parsed results
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>>> quoted_string.parse_string("'Now is the Winter of our Discontent'")
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ParseResults(["'Now is the Winter of our Discontent'"], {})
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>>> # use remove_quotes to strip quotation marks from parsed results
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>>> dequoted = quoted_string().set_parse_action(remove_quotes)
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>>> dequoted.parse_string("'Now is the Winter of our Discontent'")
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ParseResults(['Now is the Winter of our Discontent'], {})
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"""
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return t[0][1:-1]
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def with_attribute(*args: tuple[str, str], **attr_dict) -> ParseAction:
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"""
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Helper to create a validating parse action to be used with start
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tags created with :class:`make_xml_tags` or
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:class:`make_html_tags`. Use ``with_attribute`` to qualify
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a starting tag with a required attribute value, to avoid false
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matches on common tags such as ``<TD>`` or ``<DIV>``.
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Call ``with_attribute`` with a series of attribute names and
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values. Specify the list of filter attributes names and values as:
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- keyword arguments, as in ``(align="right")``, or
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- as an explicit dict with ``**`` operator, when an attribute
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name is also a Python reserved word, as in ``**{"class":"Customer", "align":"right"}``
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- a list of name-value tuples, as in ``(("ns1:class", "Customer"), ("ns2:align", "right"))``
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For attribute names with a namespace prefix, you must use the second
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form. Attribute names are matched insensitive to upper/lower case.
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If just testing for ``class`` (with or without a namespace), use
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:class:`with_class`.
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To verify that the attribute exists, but without specifying a value,
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pass ``with_attribute.ANY_VALUE`` as the value.
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The next two examples use the following input data and tag parsers:
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.. testcode::
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html = '''
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<div>
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Some text
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<div type="grid">1 4 0 1 0</div>
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<div type="graph">1,3 2,3 1,1</div>
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<div>this has no type</div>
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</div>
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'''
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div,div_end = make_html_tags("div")
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Only match div tag having a type attribute with value "grid":
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.. testcode::
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div_grid = div().set_parse_action(with_attribute(type="grid"))
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grid_expr = div_grid + SkipTo(div | div_end)("body")
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for grid_header in grid_expr.search_string(html):
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print(grid_header.body)
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prints:
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.. testoutput::
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1 4 0 1 0
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Construct a match with any div tag having a type attribute,
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regardless of the value:
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.. testcode::
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div_any_type = div().set_parse_action(
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with_attribute(type=with_attribute.ANY_VALUE)
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)
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div_expr = div_any_type + SkipTo(div | div_end)("body")
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for div_header in div_expr.search_string(html):
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print(div_header.body)
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prints:
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.. testoutput::
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1 4 0 1 0
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1,3 2,3 1,1
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"""
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attrs_list: list[tuple[str, str]] = []
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if args:
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attrs_list.extend(args)
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else:
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attrs_list.extend(attr_dict.items())
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def pa(s: str, l: int, tokens: ParseResults) -> None:
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for attrName, attrValue in attrs_list:
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if attrName not in tokens:
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raise ParseException(s, l, "no matching attribute " + attrName)
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if attrValue != with_attribute.ANY_VALUE and tokens[attrName] != attrValue: # type: ignore [attr-defined]
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raise ParseException(
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s,
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l,
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f"attribute {attrName!r} has value {tokens[attrName]!r}, must be {attrValue!r}",
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)
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return pa
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with_attribute.ANY_VALUE = object() # type: ignore [attr-defined]
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def with_class(classname: str, namespace: str = "") -> ParseAction:
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"""
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Simplified version of :meth:`with_attribute` when
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matching on a div class - made difficult because ``class`` is
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a reserved word in Python.
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Using similar input data to the :meth:`with_attribute` examples:
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.. testcode::
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html = '''
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<div>
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Some text
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<div class="grid">1 4 0 1 0</div>
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<div class="graph">1,3 2,3 1,1</div>
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<div>this <div> has no class</div>
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</div>
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'''
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div,div_end = make_html_tags("div")
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Only match div tag having the "grid" class:
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.. testcode::
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div_grid = div().set_parse_action(with_class("grid"))
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grid_expr = div_grid + SkipTo(div | div_end)("body")
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for grid_header in grid_expr.search_string(html):
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print(grid_header.body)
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prints:
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.. testoutput::
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1 4 0 1 0
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Construct a match with any div tag having a class attribute,
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regardless of the value:
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.. testcode::
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div_any_type = div().set_parse_action(
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with_class(withAttribute.ANY_VALUE)
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)
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div_expr = div_any_type + SkipTo(div | div_end)("body")
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for div_header in div_expr.search_string(html):
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print(div_header.body)
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prints:
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.. testoutput::
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1 4 0 1 0
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1,3 2,3 1,1
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"""
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classattr = f"{namespace}:class" if namespace else "class"
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return with_attribute(**{classattr: classname})
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# Compatibility synonyms
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# fmt: off
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replaceWith = replaced_by_pep8("replaceWith", replace_with)
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removeQuotes = replaced_by_pep8("removeQuotes", remove_quotes)
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withAttribute = replaced_by_pep8("withAttribute", with_attribute)
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withClass = replaced_by_pep8("withClass", with_class)
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matchOnlyAtCol = replaced_by_pep8("matchOnlyAtCol", match_only_at_col)
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# fmt: on
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