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# Copyright (c) 2016-2018 Claudiu Popa <pcmanticore@gmail.com>
# Licensed under the LGPL: https://www.gnu.org/licenses/old-licenses/lgpl-2.1.en.html
# For details: https://github.com/PyCQA/astroid/blob/master/COPYING.LESSER
"""Contains logic for retrieving special methods.
This implementation does not rely on the dot attribute access
logic, found in ``.getattr()``. The difference between these two
is that the dunder methods are looked with the type slots
(you can find more about these here
http://lucumr.pocoo.org/2014/8/16/the-python-i-would-like-to-see/)
As such, the lookup for the special methods is actually simpler than
the dot attribute access.
"""
import itertools
import astroid
from astroid import exceptions
def _lookup_in_mro(node, name):
attrs = node.locals.get(name, [])
nodes = itertools.chain.from_iterable(
ancestor.locals.get(name, []) for ancestor in node.ancestors(recurs=True)
)
values = list(itertools.chain(attrs, nodes))
if not values:
raise exceptions.AttributeInferenceError(attribute=name, target=node)
return values
def lookup(node, name):
"""Lookup the given special method name in the given *node*
If the special method was found, then a list of attributes
will be returned. Otherwise, `astroid.AttributeInferenceError`
is going to be raised.
"""
if isinstance(
node, (astroid.List, astroid.Tuple, astroid.Const, astroid.Dict, astroid.Set)
):
return _builtin_lookup(node, name)
if isinstance(node, astroid.Instance):
return _lookup_in_mro(node, name)
if isinstance(node, astroid.ClassDef):
return _class_lookup(node, name)
raise exceptions.AttributeInferenceError(attribute=name, target=node)
def _class_lookup(node, name):
metaclass = node.metaclass()
if metaclass is None:
raise exceptions.AttributeInferenceError(attribute=name, target=node)
return _lookup_in_mro(metaclass, name)
def _builtin_lookup(node, name):
values = node.locals.get(name, [])
if not values:
raise exceptions.AttributeInferenceError(attribute=name, target=node)
return values
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