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Simplify dataclass example in item loader docs

This commit is contained in:
Eugenio Lacuesta 2020-06-30 12:18:21 -03:00
parent e46b47c365
commit 5b88c522ac
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1 changed files with 6 additions and 18 deletions
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docs/topics/loaders.rst
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@ -88,29 +88,17 @@ item loaders: unless a pre-populated item is passed to the loader, fields
will be populated incrementally using the loader's :meth:`~ItemLoader.add_xpath`,
:meth:`~ItemLoader.add_css` and :meth:`~ItemLoader.add_value` methods.
Given the way that item loaders store data internally, one approach
to overcome this is to define items using the :func:`~dataclasses.field`
function, with ``list`` as the ``default_factory`` argument::
One approach to overcome this is to define items using the
:func:`~dataclasses.field` function, with a ``default`` argument::
from dataclasses import dataclass, field
from typing import Optional
@dataclass
class InventoryItem:
name: str = field(default_factory=list)
price: float = field(default_factory=list)
stock: int = field(default_factory=list)
Note that in order to keep the example simple, the types do not match
completely. A more accurate but verbose definition would be::
from dataclasses import dataclass, field
from typing import List, Union
@dataclass
class InventoryItem:
name: Union[str, List[str]] = field(default_factory=list)
price: Union[float, List[float]] = field(default_factory=list)
stock: Union[int, List[int]] = field(default_factory=list)
name: Optional[str] = field(default=None)
price: Optional[float] = field(default=None)
stock: Optional[int] = field(default=None)
.. _topics-loaders-processors: