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Item Fields Reference

Item Fields can be used to specify the type of each Item attribute and its default value. For example:

from scrapy.contrib_exp.newitem import Item, fields

class NewsItem(Item):
    content = fields.TextField()
    author = fields.TextField(default='Myself')
    published = fields.DateField()
    views = fields.IntegerField(default=0)

Fields which contain a default value will always return that value when not set, while fields which don't contain a default value will always return None when not set:

>>> it = NewsItem()
>>> it.content is None
True
>>> it.author
'Myself'
>>> it.published is None
True
>>> it.views
0

All field classes are subclasses of the :class:`BaseField` class which you can also subclass to create your own custom fields. But you can also subclass a more specific field class, say :class:`DecimalField`, to implement a PriceField, for example.

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.. module:: scrapy.contrib_exp.newitem.fields

BaseField class

The base class for all fields. It only provides code for handling default values, not any particular type. It cannot be used directly either, as its :meth:`BaseField.to_python` method is not implemented.

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The default argument (if given) must be of the type expected by this field, or any type that is accepted by the :meth:BaseField.to_python method of this field.

For example:

class NewsItem(Item):
    content = fields.TextField() # correct, no default value
    author = fields.TextField(default='Myself") # correct, with default value
    published = fields.DateField(default=23) # wrong default type (will raise TypeError)

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.. method:: to_python(value)

   Convert the input value to the type expected by this field and return
   it.

   For example, :class:`IntegerField` would convert ``'1'`` to ``1``, while
   :class:`DecimalField` would convert ``'1'`` to ``Decimal('1')`` and so
   on.

   This method is not implemented in the :class:`BaseField` class, so it
   must always be implemented in all its subclasses, in order to be usable.

   This method should raise ``TypeError`` if the input type is not
   supported, and ``ValueError`` if the input type is support but its value
   is not appropriate (for example, an integer outside a given range).

   This method must always return object of the expected field type.

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.. method:: get_default()

   Return the default value for this field, or ``None`` if the field
   doesn't specify any.

Available built-in Fields

TextField

A unicode text.

IntegerField

An integer.

DecimalField

A fixed-precision decimal number, represented in Python by a Decimal instance.

FloatField

A floating-point number represented in Python by a float instance.

BooleanField

A boolean (true/false) field.

DateTimeField

A date with time, represented in Python by a datetime.datetime instance.

DateField

A date, represented in Python by a datetime.date instance.

TimeField

A time, represented in Python by a datetime.time instance.

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