name : dunder_lookup.py # Licensed under the LGPL: https://www.gnu.org/licenses/old-licenses/lgpl-2.1.en.html # For details: https://github.com/PyCQA/astroid/blob/main/LICENSE # Copyright (c) https://github.com/PyCQA/astroid/blob/main/CONTRIBUTORS.txt """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.exceptions import AttributeInferenceError def _lookup_in_mro(node, name) -> list: 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 AttributeInferenceError(attribute=name, target=node) return values def lookup(node, name) -> list: """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 AttributeInferenceError(attribute=name, target=node) def _class_lookup(node, name) -> list: metaclass = node.metaclass() if metaclass is None: raise AttributeInferenceError(attribute=name, target=node) return _lookup_in_mro(metaclass, name) def _builtin_lookup(node, name) -> list: values = node.locals.get(name, []) if not values: raise AttributeInferenceError(attribute=name, target=node) return values