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"""
Helper functions for serializing (and deserializing) requests.
"""
import inspect
from scrapy.http import Request
from scrapy.utils.python import to_unicode
from scrapy.utils.misc import load_object
def request_to_dict(request, spider=None):
"""Convert Request object to a dict.
If a spider is given, it will try to find out the name of the spider method
used in the callback and store that as the callback.
"""
cb = request.callback
if callable(cb):
cb = _find_method(spider, cb)
eb = request.errback
if callable(eb):
eb = _find_method(spider, eb)
d = {
'url': to_unicode(request.url), # urls should be safe (safe_string_url)
'callback': cb,
'errback': eb,
'method': request.method,
'headers': dict(request.headers),
'body': request.body,
'cookies': request.cookies,
'meta': request.meta,
'_encoding': request._encoding,
'priority': request.priority,
'dont_filter': request.dont_filter,
'flags': request.flags,
'cb_kwargs': request.cb_kwargs,
}
if type(request) is not Request:
d['_class'] = request.__module__ + '.' + request.__class__.__name__
return d
def request_from_dict(d, spider=None):
"""Create Request object from a dict.
If a spider is given, it will try to resolve the callbacks looking at the
spider for methods with the same name.
"""
cb = d['callback']
if cb and spider:
cb = _get_method(spider, cb)
eb = d['errback']
if eb and spider:
eb = _get_method(spider, eb)
request_cls = load_object(d['_class']) if '_class' in d else Request
return request_cls(
url=to_unicode(d['url']),
callback=cb,
errback=eb,
method=d['method'],
headers=d['headers'],
body=d['body'],
cookies=d['cookies'],
meta=d['meta'],
encoding=d['_encoding'],
priority=d['priority'],
dont_filter=d['dont_filter'],
flags=d.get('flags'),
cb_kwargs=d.get('cb_kwargs'),
)
def _find_method(obj, func):
# Only instance methods contain ``__func__``
if obj and hasattr(func, '__func__'):
members = inspect.getmembers(obj, predicate=inspect.ismethod)
for name, obj_func in members:
# We need to use __func__ to access the original
# function object because instance method objects
# are generated each time attribute is retrieved from
# instance.
#
# Reference: The standard type hierarchy
# https://docs.python.org/3/reference/datamodel.html
if obj_func.__func__ is func.__func__:
return name
raise ValueError(f"Function {func} is not an instance method in: {obj}")
def _get_method(obj, name):
name = str(name)
try:
return getattr(obj, name)
except AttributeError:
raise ValueError(f"Method {name!r} not found in: {obj}")
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