mirror of https://github.com/scrapy/scrapy.git
136 lines
3.9 KiB
Python
136 lines
3.9 KiB
Python
"""
|
|
Scrapy Item
|
|
|
|
See documentation in docs/topics/item.rst
|
|
"""
|
|
|
|
from abc import ABCMeta
|
|
from collections.abc import MutableMapping
|
|
from copy import deepcopy
|
|
from pprint import pformat
|
|
from warnings import warn
|
|
|
|
import six
|
|
|
|
from scrapy.utils.deprecate import ScrapyDeprecationWarning
|
|
from scrapy.utils.trackref import object_ref
|
|
|
|
|
|
class BaseItem(object_ref):
|
|
"""Base class for all scraped items.
|
|
|
|
In Scrapy, an object is considered an *item* if it is an instance of either
|
|
:class:`BaseItem` or :class:`dict`. For example, when the output of a
|
|
spider callback is evaluated, only instances of :class:`BaseItem` or
|
|
:class:`dict` are passed to :ref:`item pipelines <topics-item-pipeline>`.
|
|
|
|
If you need instances of a custom class to be considered items by Scrapy,
|
|
you must inherit from either :class:`BaseItem` or :class:`dict`.
|
|
|
|
Unlike instances of :class:`dict`, instances of :class:`BaseItem` may be
|
|
:ref:`tracked <topics-leaks-trackrefs>` to debug memory leaks.
|
|
"""
|
|
pass
|
|
|
|
|
|
class Field(dict):
|
|
"""Container of field metadata"""
|
|
|
|
|
|
class ItemMeta(ABCMeta):
|
|
"""Metaclass_ of :class:`Item` that handles field definitions.
|
|
|
|
.. _metaclass: https://realpython.com/python-metaclasses
|
|
"""
|
|
|
|
def __new__(mcs, class_name, bases, attrs):
|
|
classcell = attrs.pop('__classcell__', None)
|
|
new_bases = tuple(base._class for base in bases if hasattr(base, '_class'))
|
|
_class = super(ItemMeta, mcs).__new__(mcs, 'x_' + class_name, new_bases, attrs)
|
|
|
|
fields = getattr(_class, 'fields', {})
|
|
new_attrs = {}
|
|
for n in dir(_class):
|
|
v = getattr(_class, n)
|
|
if isinstance(v, Field):
|
|
fields[n] = v
|
|
elif n in attrs:
|
|
new_attrs[n] = attrs[n]
|
|
|
|
new_attrs['fields'] = fields
|
|
new_attrs['_class'] = _class
|
|
if classcell is not None:
|
|
new_attrs['__classcell__'] = classcell
|
|
return super(ItemMeta, mcs).__new__(mcs, class_name, bases, new_attrs)
|
|
|
|
|
|
class DictItem(MutableMapping, BaseItem):
|
|
|
|
fields = {}
|
|
|
|
def __new__(cls, *args, **kwargs):
|
|
if issubclass(cls, DictItem) and not issubclass(cls, Item):
|
|
warn('scrapy.item.DictItem is deprecated, please use '
|
|
'scrapy.item.Item instead',
|
|
ScrapyDeprecationWarning, stacklevel=2)
|
|
return super(DictItem, cls).__new__(cls, *args, **kwargs)
|
|
|
|
def __init__(self, *args, **kwargs):
|
|
self._values = {}
|
|
if args or kwargs: # avoid creating dict for most common case
|
|
for k, v in six.iteritems(dict(*args, **kwargs)):
|
|
self[k] = v
|
|
|
|
def __getitem__(self, key):
|
|
return self._values[key]
|
|
|
|
def __setitem__(self, key, value):
|
|
if key in self.fields:
|
|
self._values[key] = value
|
|
else:
|
|
raise KeyError("%s does not support field: %s" %
|
|
(self.__class__.__name__, key))
|
|
|
|
def __delitem__(self, key):
|
|
del self._values[key]
|
|
|
|
def __getattr__(self, name):
|
|
if name in self.fields:
|
|
raise AttributeError("Use item[%r] to get field value" % name)
|
|
raise AttributeError(name)
|
|
|
|
def __setattr__(self, name, value):
|
|
if not name.startswith('_'):
|
|
raise AttributeError("Use item[%r] = %r to set field value" %
|
|
(name, value))
|
|
super(DictItem, self).__setattr__(name, value)
|
|
|
|
def __len__(self):
|
|
return len(self._values)
|
|
|
|
def __iter__(self):
|
|
return iter(self._values)
|
|
|
|
__hash__ = BaseItem.__hash__
|
|
|
|
def keys(self):
|
|
return self._values.keys()
|
|
|
|
def __repr__(self):
|
|
return pformat(dict(self))
|
|
|
|
def copy(self):
|
|
return self.__class__(self)
|
|
|
|
def deepcopy(self):
|
|
"""Return a `deep copy`_ of this item.
|
|
|
|
.. _deep copy: https://docs.python.org/library/copy.html#copy.deepcopy
|
|
"""
|
|
return deepcopy(self)
|
|
|
|
|
|
@six.add_metaclass(ItemMeta)
|
|
class Item(DictItem):
|
|
pass
|