151 lines
4.5 KiB
Python
151 lines
4.5 KiB
Python
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from collections import MutableMapping
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try:
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from thread import get_ident
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except ImportError:
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from _thread import get_ident
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def recursive_repr(fillvalue='...'):
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'Decorator to make a repr function return fillvalue for a recursive call'
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def decorating_function(user_function):
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repr_running = set()
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def wrapper(self):
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key = id(self), get_ident()
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if key in repr_running:
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return fillvalue
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repr_running.add(key)
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try:
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result = user_function(self)
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finally:
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repr_running.discard(key)
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return result
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# Can't use functools.wraps() here because of bootstrap issues
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wrapper.__module__ = getattr(user_function, '__module__')
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wrapper.__doc__ = getattr(user_function, '__doc__')
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wrapper.__name__ = getattr(user_function, '__name__')
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return wrapper
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return decorating_function
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class ChainMap(MutableMapping):
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""" A ChainMap groups multiple dicts (or other mappings) together
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to create a single, updatable view.
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The underlying mappings are stored in a list. That list is public and can
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be accessed / updated using the *maps* attribute. There is no other state.
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Lookups search the underlying mappings successively until a key is found.
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In contrast, writes, updates, and deletions only operate on the first
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mapping.
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"""
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def __init__(self, *maps):
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"""Initialize a ChainMap by setting *maps* to the given mappings.
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If no mappings are provided, a single empty dictionary is used.
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"""
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self.maps = list(maps) or [{}] # always at least one map
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def __missing__(self, key):
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raise KeyError(key)
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def __getitem__(self, key):
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for mapping in self.maps:
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try:
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# can't use 'key in mapping' with defaultdict
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return mapping[key]
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except KeyError:
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pass
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# support subclasses that define __missing__
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return self.__missing__(key)
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def get(self, key, default=None):
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return self[key] if key in self else default
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def __len__(self):
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# reuses stored hash values if possible
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return len(set().union(*self.maps))
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def __iter__(self):
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return iter(set().union(*self.maps))
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def __contains__(self, key):
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return any(key in m for m in self.maps)
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def __bool__(self):
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return any(self.maps)
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@recursive_repr()
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def __repr__(self):
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return '{0.__class__.__name__}({1})'.format(
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self, ', '.join(repr(m) for m in self.maps))
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@classmethod
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def fromkeys(cls, iterable, *args):
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'Create a ChainMap with a single dict created from the iterable.'
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return cls(dict.fromkeys(iterable, *args))
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def copy(self):
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"""
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New ChainMap or subclass with a new copy of maps[0] and refs to
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maps[1:]
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"""
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return self.__class__(self.maps[0].copy(), *self.maps[1:])
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__copy__ = copy
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def new_child(self, m=None): # like Django's Context.push()
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"""
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New ChainMap with a new map followed by all previous maps. If no
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map is provided, an empty dict is used.
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"""
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if m is None:
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m = {}
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return self.__class__(m, *self.maps)
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@property
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def parents(self): # like Django's Context.pop()
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'New ChainMap from maps[1:].'
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return self.__class__(*self.maps[1:])
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def __setitem__(self, key, value):
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self.maps[0][key] = value
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def __delitem__(self, key):
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try:
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del self.maps[0][key]
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except KeyError:
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raise KeyError('Key not found in the first mapping: {!r}'
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.format(key))
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def popitem(self):
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"""
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Remove and return an item pair from maps[0]. Raise KeyError is maps[0]
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is empty.
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"""
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try:
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return self.maps[0].popitem()
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except KeyError:
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raise KeyError('No keys found in the first mapping.')
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def pop(self, key, *args):
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"""
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Remove *key* from maps[0] and return its value. Raise KeyError if
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*key* not in maps[0].
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"""
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try:
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return self.maps[0].pop(key, *args)
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except KeyError:
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raise KeyError('Key not found in the first mapping: {!r}'
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.format(key))
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def clear(self):
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'Clear maps[0], leaving maps[1:] intact.'
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self.maps[0].clear()
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