Source code for parsel.selector

"""
XPath selectors based on lxml
"""

import typing
from typing import Any, Dict, List, Optional, Mapping, Pattern, Union

from lxml import etree, html

from .utils import flatten, iflatten, extract_regex, shorten
from .csstranslator import HTMLTranslator, GenericTranslator

_SelectorType = typing.TypeVar("_SelectorType", bound="Selector")


[docs]class CannotRemoveElementWithoutRoot(Exception): pass
[docs]class CannotRemoveElementWithoutParent(Exception): pass
[docs]class SafeXMLParser(etree.XMLParser): def __init__(self, *args, **kwargs) -> None: kwargs.setdefault("resolve_entities", False) super().__init__(*args, **kwargs)
_ctgroup = { "html": { "_parser": html.HTMLParser, "_csstranslator": HTMLTranslator(), "_tostring_method": "html", }, "xml": { "_parser": SafeXMLParser, "_csstranslator": GenericTranslator(), "_tostring_method": "xml", }, } def _st(st: Optional[str]) -> str: if st is None: return "html" elif st in _ctgroup: return st else: raise ValueError(f"Invalid type: {st}")
[docs]def create_root_node(text, parser_cls, base_url=None): """Create root node for text using given parser class.""" body = text.strip().replace("\x00", "").encode("utf8") or b"<html/>" parser = parser_cls(recover=True, encoding="utf8") root = etree.fromstring(body, parser=parser, base_url=base_url) if root is None: root = etree.fromstring(b"<html/>", parser=parser, base_url=base_url) return root
[docs]class SelectorList(List[_SelectorType]): """ The :class:`SelectorList` class is a subclass of the builtin ``list`` class, which provides a few additional methods. """ @typing.overload def __getitem__(self, pos: int) -> _SelectorType: pass @typing.overload def __getitem__(self, pos: slice) -> "SelectorList[_SelectorType]": pass def __getitem__( self, pos: Union[int, slice] ) -> Union[_SelectorType, "SelectorList[_SelectorType]"]: o = super().__getitem__(pos) return self.__class__(o) if isinstance(pos, slice) else o def __getstate__(self) -> None: raise TypeError("can't pickle SelectorList objects")
[docs] def xpath( self, xpath: str, namespaces: Optional[Mapping[str, str]] = None, **kwargs, ) -> "SelectorList[_SelectorType]": """ Call the ``.xpath()`` method for each element in this list and return their results flattened as another :class:`SelectorList`. ``query`` is the same argument as the one in :meth:`Selector.xpath` ``namespaces`` is an optional ``prefix: namespace-uri`` mapping (dict) for additional prefixes to those registered with ``register_namespace(prefix, uri)``. Contrary to ``register_namespace()``, these prefixes are not saved for future calls. Any additional named arguments can be used to pass values for XPath variables in the XPath expression, e.g.:: selector.xpath('//a[href=$url]', url="http://www.example.com") """ return self.__class__( flatten([x.xpath(xpath, namespaces=namespaces, **kwargs) for x in self]) )
[docs] def css(self, query: str) -> "SelectorList[_SelectorType]": """ Call the ``.css()`` method for each element in this list and return their results flattened as another :class:`SelectorList`. ``query`` is the same argument as the one in :meth:`Selector.css` """ return self.__class__(flatten([x.css(query) for x in self]))
[docs] def re( self, regex: Union[str, Pattern[str]], replace_entities: bool = True ) -> List[str]: """ Call the ``.re()`` method for each element in this list and return their results flattened, as a list of strings. By default, character entity references are replaced by their corresponding character (except for ``&amp;`` and ``&lt;``. Passing ``replace_entities`` as ``False`` switches off these replacements. """ return flatten([x.re(regex, replace_entities=replace_entities) for x in self])
@typing.overload def re_first( self, regex: Union[str, Pattern[str]], default: None = None, replace_entities: bool = True, ) -> Optional[str]: pass @typing.overload def re_first( self, regex: Union[str, Pattern[str]], default: str, replace_entities: bool = True, ) -> str: pass
[docs] def re_first( self, regex: Union[str, Pattern[str]], default: Optional[str] = None, replace_entities: bool = True, ) -> Optional[str]: """ Call the ``.re()`` method for the first element in this list and return the result in an string. If the list is empty or the regex doesn't match anything, return the default value (``None`` if the argument is not provided). By default, character entity references are replaced by their corresponding character (except for ``&amp;`` and ``&lt;``. Passing ``replace_entities`` as ``False`` switches off these replacements. """ for el in iflatten( x.re(regex, replace_entities=replace_entities) for x in self ): return el return default
[docs] def getall(self) -> List[str]: """ Call the ``.get()`` method for each element is this list and return their results flattened, as a list of strings. """ return [x.get() for x in self]
extract = getall @typing.overload def get(self, default: None = None) -> Optional[str]: pass @typing.overload def get(self, default: str) -> str: pass
[docs] def get(self, default: Optional[str] = None) -> Optional[str]: """ Return the result of ``.get()`` for the first element in this list. If the list is empty, return the default value. """ for x in self: return x.get() return default
extract_first = get @property def attrib(self) -> Mapping[str, str]: """Return the attributes dictionary for the first element. If the list is empty, return an empty dict. """ for x in self: return x.attrib return {}
[docs] def remove(self) -> None: """ Remove matched nodes from the parent for each element in this list. """ for x in self: x.remove()
[docs]class Selector: """ :class:`Selector` allows you to select parts of an XML or HTML text using CSS or XPath expressions and extract data from it. ``text`` is a `str`` object ``type`` defines the selector type, it can be ``"html"``, ``"xml"`` or ``None`` (default). If ``type`` is ``None``, the selector defaults to ``"html"``. ``base_url`` allows setting a URL for the document. This is needed when looking up external entities with relative paths. See [`lxml` documentation](https://lxml.de/api/index.html) ``lxml.etree.fromstring`` for more information. """ __slots__ = [ "text", "namespaces", "type", "_expr", "root", "__weakref__", "_parser", "_csstranslator", "_tostring_method", ] _default_type: Optional[str] = None _default_namespaces = { "re": "http://exslt.org/regular-expressions", # supported in libxslt: # set:difference # set:has-same-node # set:intersection # set:leading # set:trailing "set": "http://exslt.org/sets", } _lxml_smart_strings = False selectorlist_cls = SelectorList["Selector"] def __init__( self, text: Optional[str] = None, type: Optional[str] = None, namespaces: Optional[Mapping[str, str]] = None, root: Optional[Any] = None, base_url: Optional[str] = None, _expr: Optional[str] = None, ) -> None: self.type = st = _st(type or self._default_type) self._parser = _ctgroup[st]["_parser"] self._csstranslator = _ctgroup[st]["_csstranslator"] self._tostring_method = _ctgroup[st]["_tostring_method"] if text is not None: if not isinstance(text, str): msg = f"text argument should be of type str, got {text.__class__}" raise TypeError(msg) root = self._get_root(text, base_url) elif root is None: raise ValueError("Selector needs either text or root argument") self.namespaces = dict(self._default_namespaces) if namespaces is not None: self.namespaces.update(namespaces) self.root = root self._expr = _expr def __getstate__(self) -> Any: raise TypeError("can't pickle Selector objects") def _get_root(self, text: str, base_url: Optional[str] = None) -> Any: return create_root_node(text, self._parser, base_url=base_url)
[docs] def xpath( self: _SelectorType, query: str, namespaces: Optional[Mapping[str, str]] = None, **kwargs, ) -> SelectorList[_SelectorType]: """ Find nodes matching the xpath ``query`` and return the result as a :class:`SelectorList` instance with all elements flattened. List elements implement :class:`Selector` interface too. ``query`` is a string containing the XPATH query to apply. ``namespaces`` is an optional ``prefix: namespace-uri`` mapping (dict) for additional prefixes to those registered with ``register_namespace(prefix, uri)``. Contrary to ``register_namespace()``, these prefixes are not saved for future calls. Any additional named arguments can be used to pass values for XPath variables in the XPath expression, e.g.:: selector.xpath('//a[href=$url]', url="http://www.example.com") """ try: xpathev = self.root.xpath except AttributeError: return self.selectorlist_cls([]) nsp = dict(self.namespaces) if namespaces is not None: nsp.update(namespaces) try: result = xpathev( query, namespaces=nsp, smart_strings=self._lxml_smart_strings, **kwargs ) except etree.XPathError as exc: raise ValueError(f"XPath error: {exc} in {query}") if type(result) is not list: result = [result] result = [ self.__class__( root=x, _expr=query, namespaces=self.namespaces, type=self.type ) for x in result ] return self.selectorlist_cls(result)
[docs] def css(self: _SelectorType, query: str) -> SelectorList[_SelectorType]: """ Apply the given CSS selector and return a :class:`SelectorList` instance. ``query`` is a string containing the CSS selector to apply. In the background, CSS queries are translated into XPath queries using `cssselect`_ library and run ``.xpath()`` method. .. _cssselect: https://pypi.python.org/pypi/cssselect/ """ return self.xpath(self._css2xpath(query))
def _css2xpath(self, query: str) -> Any: return self._csstranslator.css_to_xpath(query)
[docs] def re( self, regex: Union[str, Pattern[str]], replace_entities: bool = True ) -> List[str]: """ Apply the given regex and return a list of strings with the matches. ``regex`` can be either a compiled regular expression or a string which will be compiled to a regular expression using ``re.compile(regex)``. By default, character entity references are replaced by their corresponding character (except for ``&amp;`` and ``&lt;``). Passing ``replace_entities`` as ``False`` switches off these replacements. """ return extract_regex(regex, self.get(), replace_entities=replace_entities)
@typing.overload def re_first( self, regex: Union[str, Pattern[str]], default: None = None, replace_entities: bool = True, ) -> Optional[str]: pass @typing.overload def re_first( self, regex: Union[str, Pattern[str]], default: str, replace_entities: bool = True, ) -> str: pass
[docs] def re_first( self, regex: Union[str, Pattern[str]], default: Optional[str] = None, replace_entities: bool = True, ) -> Optional[str]: """ Apply the given regex and return the first string which matches. If there is no match, return the default value (``None`` if the argument is not provided). By default, character entity references are replaced by their corresponding character (except for ``&amp;`` and ``&lt;``). Passing ``replace_entities`` as ``False`` switches off these replacements. """ return next( iflatten(self.re(regex, replace_entities=replace_entities)), default )
[docs] def get(self) -> str: """ Serialize and return the matched nodes in a single string. Percent encoded content is unquoted. """ try: return etree.tostring( self.root, method=self._tostring_method, encoding="unicode", with_tail=False, ) except (AttributeError, TypeError): if self.root is True: return "1" elif self.root is False: return "0" else: return str(self.root)
extract = get
[docs] def getall(self) -> List[str]: """ Serialize and return the matched node in a 1-element list of strings. """ return [self.get()]
[docs] def register_namespace(self, prefix: str, uri: str) -> None: """ Register the given namespace to be used in this :class:`Selector`. Without registering namespaces you can't select or extract data from non-standard namespaces. See :ref:`selector-examples-xml`. """ self.namespaces[prefix] = uri
[docs] def remove_namespaces(self) -> None: """ Remove all namespaces, allowing to traverse the document using namespace-less xpaths. See :ref:`removing-namespaces`. """ for el in self.root.iter("*"): if el.tag.startswith("{"): el.tag = el.tag.split("}", 1)[1] # loop on element attributes also for an in el.attrib: if an.startswith("{"): el.attrib[an.split("}", 1)[1]] = el.attrib.pop(an) # remove namespace declarations etree.cleanup_namespaces(self.root)
[docs] def remove(self) -> None: """ Remove matched nodes from the parent element. """ try: parent = self.root.getparent() except AttributeError: # 'str' object has no attribute 'getparent' raise CannotRemoveElementWithoutRoot( "The node you're trying to remove has no root, " "are you trying to remove a pseudo-element? " "Try to use 'li' as a selector instead of 'li::text' or " "'//li' instead of '//li/text()', for example." ) try: parent.remove(self.root) except AttributeError: # 'NoneType' object has no attribute 'remove' raise CannotRemoveElementWithoutParent( "The node you're trying to remove has no parent, " "are you trying to remove a root element?" )
@property def attrib(self) -> Dict[str, str]: """Return the attributes dictionary for underlying element.""" return dict(self.root.attrib) def __bool__(self) -> bool: """ Return ``True`` if there is any real content selected or ``False`` otherwise. In other words, the boolean value of a :class:`Selector` is given by the contents it selects. """ return bool(self.get()) __nonzero__ = __bool__ def __str__(self) -> str: data = repr(shorten(self.get(), width=40)) return f"<{type(self).__name__} xpath={self._expr!r} data={data}>" __repr__ = __str__