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"""
This module contains a simple class (Libxml2Document) which provides cache and
garbage collection to libxml2 documents (xmlDoc).
"""
import weakref
from scrapy.utils.trackref import object_ref
from .factories import xmlDoc_from_html
class Libxml2Document(object_ref):
cache = weakref.WeakKeyDictionary()
__slots__ = ['xmlDoc', 'xpathContext', '__weakref__']
def __new__(cls, response, factory=xmlDoc_from_html):
cache = cls.cache.setdefault(response, {})
if factory not in cache:
obj = object_ref.__new__(cls)
obj.xmlDoc = factory(response)
obj.xpathContext = obj.xmlDoc.xpathNewContext()
cache[factory] = obj
return cache[factory]
def __del__(self):
# we must call both cleanup functions, so we try/except all exceptions
# to make sure one doesn't prevent the other from being called
# this call sometimes raises a "NoneType is not callable" TypeError
# so the try/except block silences them
try:
self.xmlDoc.freeDoc()
except:
pass
try:
self.xpathContext.xpathFreeContext()
except:
pass
def __str__(self):
return "<Libxml2Document %s>" % self.xmlDoc.name
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