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102 lines
2.6 KiB
102 lines
2.6 KiB
"""
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Scrapy Item
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See documentation in docs/topics/item.rst
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"""
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from pprint import pformat
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from collections import MutableMapping
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from abc import ABCMeta
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import six
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from scrapy.utils.trackref import object_ref
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class BaseItem(object_ref):
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"""Base class for all scraped items."""
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pass
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class Field(dict):
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"""Container of field metadata"""
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class ItemMeta(ABCMeta):
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def __new__(mcs, class_name, bases, attrs):
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classcell = attrs.pop('__classcell__', None)
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new_bases = tuple(base._class for base in bases if hasattr(base, '_class'))
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_class = super(ItemMeta, mcs).__new__(mcs, 'x_' + class_name, new_bases, attrs)
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fields = getattr(_class, 'fields', {})
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new_attrs = {}
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for n in dir(_class):
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v = getattr(_class, n)
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if isinstance(v, Field):
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fields[n] = v
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elif n in attrs:
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new_attrs[n] = attrs[n]
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new_attrs['fields'] = fields
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new_attrs['_class'] = _class
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if classcell is not None:
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new_attrs['__classcell__'] = classcell
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return super(ItemMeta, mcs).__new__(mcs, class_name, bases, new_attrs)
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class DictItem(MutableMapping, BaseItem):
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fields = {}
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def __init__(self, *args, **kwargs):
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self._values = {}
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if args or kwargs: # avoid creating dict for most common case
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for k, v in six.iteritems(dict(*args, **kwargs)):
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self[k] = v
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def __getitem__(self, key):
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return self._values[key]
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def __setitem__(self, key, value):
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if key in self.fields:
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self._values[key] = value
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else:
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raise KeyError("%s does not support field: %s" %
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(self.__class__.__name__, key))
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def __delitem__(self, key):
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del self._values[key]
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def __getattr__(self, name):
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if name in self.fields:
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raise AttributeError("Use item[%r] to get field value" % name)
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raise AttributeError(name)
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def __setattr__(self, name, value):
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if not name.startswith('_'):
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raise AttributeError("Use item[%r] = %r to set field value" %
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(name, value))
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super(DictItem, self).__setattr__(name, value)
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def __len__(self):
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return len(self._values)
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def __iter__(self):
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return iter(self._values)
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__hash__ = BaseItem.__hash__
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def keys(self):
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return self._values.keys()
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def __repr__(self):
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return pformat(dict(self))
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def copy(self):
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return self.__class__(self)
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@six.add_metaclass(ItemMeta)
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class Item(DictItem):
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pass
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