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Filename :
_pset.py
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from ._compat import Set, Hashable import sys from pyrsistent._pmap import pmap PY2 = sys.version_info[0] < 3 class PSet(object): """ Persistent set implementation. Built on top of the persistent map. The set supports all operations in the Set protocol and is Hashable. Do not instantiate directly, instead use the factory functions :py:func:`s` or :py:func:`pset` to create an instance. Random access and insert is log32(n) where n is the size of the set. Some examples: >>> s = pset([1, 2, 3, 1]) >>> s2 = s.add(4) >>> s3 = s2.remove(2) >>> s pset([1, 2, 3]) >>> s2 pset([1, 2, 3, 4]) >>> s3 pset([1, 3, 4]) """ __slots__ = ('_map', '__weakref__') def __new__(cls, m): self = super(PSet, cls).__new__(cls) self._map = m return self def __contains__(self, element): return element in self._map def __iter__(self): return iter(self._map) def __len__(self): return len(self._map) def __repr__(self): if PY2 or not self: return 'p' + str(set(self)) return 'pset([{0}])'.format(str(set(self))[1:-1]) def __str__(self): return self.__repr__() def __hash__(self): return hash(self._map) def __reduce__(self): # Pickling support return pset, (list(self),) @classmethod def _from_iterable(cls, it, pre_size=8): return PSet(pmap(dict((k, True) for k in it), pre_size=pre_size)) def add(self, element): """ Return a new PSet with element added >>> s1 = s(1, 2) >>> s1.add(3) pset([1, 2, 3]) """ return self.evolver().add(element).persistent() def update(self, iterable): """ Return a new PSet with elements in iterable added >>> s1 = s(1, 2) >>> s1.update([3, 4, 4]) pset([1, 2, 3, 4]) """ e = self.evolver() for element in iterable: e.add(element) return e.persistent() def remove(self, element): """ Return a new PSet with element removed. Raises KeyError if element is not present. >>> s1 = s(1, 2) >>> s1.remove(2) pset([1]) """ if element in self._map: return self.evolver().remove(element).persistent() raise KeyError("Element '%s' not present in PSet" % element) def discard(self, element): """ Return a new PSet with element removed. Returns itself if element is not present. """ if element in self._map: return self.evolver().remove(element).persistent() return self class _Evolver(object): __slots__ = ('_original_pset', '_pmap_evolver') def __init__(self, original_pset): self._original_pset = original_pset self._pmap_evolver = original_pset._map.evolver() def add(self, element): self._pmap_evolver[element] = True return self def remove(self, element): del self._pmap_evolver[element] return self def is_dirty(self): return self._pmap_evolver.is_dirty() def persistent(self): if not self.is_dirty(): return self._original_pset return PSet(self._pmap_evolver.persistent()) def __len__(self): return len(self._pmap_evolver) def copy(self): return self def evolver(self): """ Create a new evolver for this pset. For a discussion on evolvers in general see the documentation for the pvector evolver. Create the evolver and perform various mutating updates to it: >>> s1 = s(1, 2, 3) >>> e = s1.evolver() >>> _ = e.add(4) >>> len(e) 4 >>> _ = e.remove(1) The underlying pset remains the same: >>> s1 pset([1, 2, 3]) The changes are kept in the evolver. An updated pmap can be created using the persistent() function on the evolver. >>> s2 = e.persistent() >>> s2 pset([2, 3, 4]) The new pset will share data with the original pset in the same way that would have been done if only using operations on the pset. """ return PSet._Evolver(self) # All the operations and comparisons you would expect on a set. # # This is not very beautiful. If we avoid inheriting from PSet we can use the # __slots__ concepts (which requires a new style class) and hopefully save some memory. __le__ = Set.__le__ __lt__ = Set.__lt__ __gt__ = Set.__gt__ __ge__ = Set.__ge__ __eq__ = Set.__eq__ __ne__ = Set.__ne__ __and__ = Set.__and__ __or__ = Set.__or__ __sub__ = Set.__sub__ __xor__ = Set.__xor__ issubset = __le__ issuperset = __ge__ union = __or__ intersection = __and__ difference = __sub__ symmetric_difference = __xor__ isdisjoint = Set.isdisjoint Set.register(PSet) Hashable.register(PSet) _EMPTY_PSET = PSet(pmap()) def pset(iterable=(), pre_size=8): """ Creates a persistent set from iterable. Optionally takes a sizing parameter equivalent to that used for :py:func:`pmap`. >>> s1 = pset([1, 2, 3, 2]) >>> s1 pset([1, 2, 3]) """ if not iterable: return _EMPTY_PSET return PSet._from_iterable(iterable, pre_size=pre_size) def s(*elements): """ Create a persistent set. Takes an arbitrary number of arguments to insert into the new set. >>> s1 = s(1, 2, 3, 2) >>> s1 pset([1, 2, 3]) """ return pset(elements)