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Ausgabe der neuen DB Einträge

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hubobel 2022-01-02 21:50:48 +01:00
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venv/lib/python3.9/site-packages/itemloaders/__init__.py Normal file
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"""
Item Loader
See documentation in docs/topics/loaders.rst
"""
from contextlib import suppress
from itemadapter import ItemAdapter
from parsel.utils import extract_regex, flatten
from itemloaders.common import wrap_loader_context
from itemloaders.processors import Identity
from itemloaders.utils import arg_to_iter
def unbound_method(method):
"""
Allow to use single-argument functions as input or output processors
(no need to define an unused first 'self' argument)
"""
with suppress(AttributeError):
if '.' not in method.__qualname__:
return method.__func__
return method
class ItemLoader:
"""
Return a new Item Loader for populating the given item. If no item is
given, one is instantiated automatically using the class in
:attr:`default_item_class`.
When instantiated with a :param ``selector`` parameter the :class:`ItemLoader` class
provides convenient mechanisms for extracting data from web pages
using parsel_ selectors.
:param item: The item instance to populate using subsequent calls to
:meth:`~ItemLoader.add_xpath`, :meth:`~ItemLoader.add_css`,
or :meth:`~ItemLoader.add_value`.
:type item: :class:`dict` object
:param selector: The selector to extract data from, when using the
:meth:`add_xpath` (resp. :meth:`add_css`) or :meth:`replace_xpath`
(resp. :meth:`replace_css`) method.
:type selector: :class:`~parsel.selector.Selector` object
The item, selector and the remaining keyword arguments are
assigned to the Loader context (accessible through the :attr:`context` attribute).
.. attribute:: item
The item object being parsed by this Item Loader.
This is mostly used as a property so when attempting to override this
value, you may want to check out :attr:`default_item_class` first.
.. attribute:: context
The currently active :ref:`Context <loaders-context>` of this Item Loader.
Refer to <loaders-context> for more information about the Loader Context.
.. attribute:: default_item_class
An Item class (or factory), used to instantiate items when not given in
the ``__init__`` method.
.. warning:: Currently, this factory/class needs to be
callable/instantiated without any arguments.
If you are using ``dataclasses``, please consider the following
alternative::
from dataclasses import dataclass, field
from typing import Optional
@dataclass
class Product:
name: Optional[str] = field(default=None)
price: Optional[float] = field(default=None)
.. attribute:: default_input_processor
The default input processor to use for those fields which don't specify
one.
.. attribute:: default_output_processor
The default output processor to use for those fields which don't specify
one.
.. attribute:: selector
The :class:`~parsel.selector.Selector` object to extract data from.
It's the selector given in the ``__init__`` method.
This attribute is meant to be read-only.
.. _parsel: https://parsel.readthedocs.io/en/latest/
"""
default_item_class = dict
default_input_processor = Identity()
default_output_processor = Identity()
def __init__(self, item=None, selector=None, parent=None, **context):
self.selector = selector
context.update(selector=selector)
if item is None:
item = self.default_item_class()
self._local_item = item
context['item'] = item
self.context = context
self.parent = parent
self._local_values = {}
# values from initial item
for field_name, value in ItemAdapter(item).items():
self._values.setdefault(field_name, [])
self._values[field_name] += arg_to_iter(value)
@property
def _values(self):
if self.parent is not None:
return self.parent._values
else:
return self._local_values
@property
def item(self):
if self.parent is not None:
return self.parent.item
else:
return self._local_item
def nested_xpath(self, xpath, **context):
"""
Create a nested loader with an xpath selector.
The supplied selector is applied relative to selector associated
with this :class:`ItemLoader`. The nested loader shares the item
with the parent :class:`ItemLoader` so calls to :meth:`add_xpath`,
:meth:`add_value`, :meth:`replace_value`, etc. will behave as expected.
"""
selector = self.selector.xpath(xpath)
context.update(selector=selector)
subloader = self.__class__(
item=self.item, parent=self, **context
)
return subloader
def nested_css(self, css, **context):
"""
Create a nested loader with a css selector.
The supplied selector is applied relative to selector associated
with this :class:`ItemLoader`. The nested loader shares the item
with the parent :class:`ItemLoader` so calls to :meth:`add_xpath`,
:meth:`add_value`, :meth:`replace_value`, etc. will behave as expected.
"""
selector = self.selector.css(css)
context.update(selector=selector)
subloader = self.__class__(
item=self.item, parent=self, **context
)
return subloader
def add_value(self, field_name, value, *processors, **kw):
"""
Process and then add the given ``value`` for the given field.
The value is first passed through :meth:`get_value` by giving the
``processors`` and ``kwargs``, and then passed through the
:ref:`field input processor <processors>` and its result
appended to the data collected for that field. If the field already
contains collected data, the new data is added.
The given ``field_name`` can be ``None``, in which case values for
multiple fields may be added. And the processed value should be a dict
with field_name mapped to values.
Examples::
loader.add_value('name', 'Color TV')
loader.add_value('colours', ['white', 'blue'])
loader.add_value('length', '100')
loader.add_value('name', 'name: foo', TakeFirst(), re='name: (.+)')
loader.add_value(None, {'name': 'foo', 'sex': 'male'})
"""
value = self.get_value(value, *processors, **kw)
if value is None:
return
if not field_name:
for k, v in value.items():
self._add_value(k, v)
else:
self._add_value(field_name, value)
def replace_value(self, field_name, value, *processors, **kw):
"""
Similar to :meth:`add_value` but replaces the collected data with the
new value instead of adding it.
"""
value = self.get_value(value, *processors, **kw)
if value is None:
return
if not field_name:
for k, v in value.items():
self._replace_value(k, v)
else:
self._replace_value(field_name, value)
def _add_value(self, field_name, value):
value = arg_to_iter(value)
processed_value = self._process_input_value(field_name, value)
if processed_value:
self._values.setdefault(field_name, [])
self._values[field_name] += arg_to_iter(processed_value)
def _replace_value(self, field_name, value):
self._values.pop(field_name, None)
self._add_value(field_name, value)
def get_value(self, value, *processors, **kw):
"""
Process the given ``value`` by the given ``processors`` and keyword
arguments.
Available keyword arguments:
:param re: a regular expression to use for extracting data from the
given value using :func:`~parsel.utils.extract_regex` method,
applied before processors
:type re: str or typing.Pattern
Examples:
>>> from itemloaders import ItemLoader
>>> from itemloaders.processors import TakeFirst
>>> loader = ItemLoader()
>>> loader.get_value('name: foo', TakeFirst(), str.upper, re='name: (.+)')
'FOO'
"""
regex = kw.get('re', None)
if regex:
value = arg_to_iter(value)
value = flatten(extract_regex(regex, x) for x in value)
for proc in processors:
if value is None:
break
_proc = proc
proc = wrap_loader_context(proc, self.context)
try:
value = proc(value)
except Exception as e:
raise ValueError("Error with processor %s value=%r error='%s: %s'" %
(_proc.__class__.__name__, value,
type(e).__name__, str(e)))
return value
def load_item(self):
"""
Populate the item with the data collected so far, and return it. The
data collected is first passed through the :ref:`output processors
<processors>` to get the final value to assign to each item field.
"""
adapter = ItemAdapter(self.item)
for field_name in tuple(self._values):
value = self.get_output_value(field_name)
if value is not None:
adapter[field_name] = value
return adapter.item
def get_output_value(self, field_name):
"""
Return the collected values parsed using the output processor, for the
given field. This method doesn't populate or modify the item at all.
"""
proc = self.get_output_processor(field_name)
proc = wrap_loader_context(proc, self.context)
value = self._values.get(field_name, [])
try:
return proc(value)
except Exception as e:
raise ValueError("Error with output processor: field=%r value=%r error='%s: %s'" %
(field_name, value, type(e).__name__, str(e)))
def get_collected_values(self, field_name):
"""Return the collected values for the given field."""
return self._values.get(field_name, [])
def get_input_processor(self, field_name):
proc = getattr(self, '%s_in' % field_name, None)
if not proc:
proc = self._get_item_field_attr(
field_name,
'input_processor',
self.default_input_processor
)
return unbound_method(proc)
def get_output_processor(self, field_name):
proc = getattr(self, '%s_out' % field_name, None)
if not proc:
proc = self._get_item_field_attr(
field_name,
'output_processor',
self.default_output_processor
)
return unbound_method(proc)
def _get_item_field_attr(self, field_name, key, default=None):
field_meta = ItemAdapter(self.item).get_field_meta(field_name)
return field_meta.get(key, default)
def _process_input_value(self, field_name, value):
proc = self.get_input_processor(field_name)
_proc = proc
proc = wrap_loader_context(proc, self.context)
try:
return proc(value)
except Exception as e:
raise ValueError(
"Error with input processor %s: field=%r value=%r "
"error='%s: %s'" % (_proc.__class__.__name__, field_name,
value, type(e).__name__, str(e)))
def _check_selector_method(self):
if self.selector is None:
raise RuntimeError(
"To use XPath or CSS selectors, %s"
"must be instantiated with a selector" % self.__class__.__name__
)
def add_xpath(self, field_name, xpath, *processors, **kw):
"""
Similar to :meth:`ItemLoader.add_value` but receives an XPath instead of a
value, which is used to extract a list of strings from the
selector associated with this :class:`ItemLoader`.
See :meth:`get_xpath` for ``kwargs``.
:param xpath: the XPath to extract data from
:type xpath: str
Examples::
# HTML snippet: <p class="product-name">Color TV</p>
loader.add_xpath('name', '//p[@class="product-name"]')
# HTML snippet: <p id="price">the price is $1200</p>
loader.add_xpath('price', '//p[@id="price"]', re='the price is (.*)')
"""
values = self._get_xpathvalues(xpath, **kw)
self.add_value(field_name, values, *processors, **kw)
def replace_xpath(self, field_name, xpath, *processors, **kw):
"""
Similar to :meth:`add_xpath` but replaces collected data instead of adding it.
"""
values = self._get_xpathvalues(xpath, **kw)
self.replace_value(field_name, values, *processors, **kw)
def get_xpath(self, xpath, *processors, **kw):
"""
Similar to :meth:`ItemLoader.get_value` but receives an XPath instead of a
value, which is used to extract a list of unicode strings from the
selector associated with this :class:`ItemLoader`.
:param xpath: the XPath to extract data from
:type xpath: str
:param re: a regular expression to use for extracting data from the
selected XPath region
:type re: str or typing.Pattern
Examples::
# HTML snippet: <p class="product-name">Color TV</p>
loader.get_xpath('//p[@class="product-name"]')
# HTML snippet: <p id="price">the price is $1200</p>
loader.get_xpath('//p[@id="price"]', TakeFirst(), re='the price is (.*)')
"""
values = self._get_xpathvalues(xpath, **kw)
return self.get_value(values, *processors, **kw)
def _get_xpathvalues(self, xpaths, **kw):
self._check_selector_method()
xpaths = arg_to_iter(xpaths)
return flatten(self.selector.xpath(xpath).getall() for xpath in xpaths)
def add_css(self, field_name, css, *processors, **kw):
"""
Similar to :meth:`ItemLoader.add_value` but receives a CSS selector
instead of a value, which is used to extract a list of unicode strings
from the selector associated with this :class:`ItemLoader`.
See :meth:`get_css` for ``kwargs``.
:param css: the CSS selector to extract data from
:type css: str
Examples::
# HTML snippet: <p class="product-name">Color TV</p>
loader.add_css('name', 'p.product-name')
# HTML snippet: <p id="price">the price is $1200</p>
loader.add_css('price', 'p#price', re='the price is (.*)')
"""
values = self._get_cssvalues(css, **kw)
self.add_value(field_name, values, *processors, **kw)
def replace_css(self, field_name, css, *processors, **kw):
"""
Similar to :meth:`add_css` but replaces collected data instead of adding it.
"""
values = self._get_cssvalues(css, **kw)
self.replace_value(field_name, values, *processors, **kw)
def get_css(self, css, *processors, **kw):
"""
Similar to :meth:`ItemLoader.get_value` but receives a CSS selector
instead of a value, which is used to extract a list of unicode strings
from the selector associated with this :class:`ItemLoader`.
:param css: the CSS selector to extract data from
:type css: str
:param re: a regular expression to use for extracting data from the
selected CSS region
:type re: str or typing.Pattern
Examples::
# HTML snippet: <p class="product-name">Color TV</p>
loader.get_css('p.product-name')
# HTML snippet: <p id="price">the price is $1200</p>
loader.get_css('p#price', TakeFirst(), re='the price is (.*)')
"""
values = self._get_cssvalues(css, **kw)
return self.get_value(values, *processors, **kw)
def _get_cssvalues(self, csss, **kw):
self._check_selector_method()
csss = arg_to_iter(csss)
return flatten(self.selector.css(css).getall() for css in csss)