chromium / native_client / src / third_party / scons-2.0.1 / refs/heads/master / . / engine / SCons / compat / _scons_sets.py

"""Classes to represent arbitrary sets (including sets of sets). | |

This module implements sets using dictionaries whose values are | |

ignored. The usual operations (union, intersection, deletion, etc.) | |

are provided as both methods and operators. | |

Important: sets are not sequences! While they support 'x in s', | |

'len(s)', and 'for x in s', none of those operations are unique for | |

sequences; for example, mappings support all three as well. The | |

characteristic operation for sequences is subscripting with small | |

integers: s[i], for i in range(len(s)). Sets don't support | |

subscripting at all. Also, sequences allow multiple occurrences and | |

their elements have a definite order; sets on the other hand don't | |

record multiple occurrences and don't remember the order of element | |

insertion (which is why they don't support s[i]). | |

The following classes are provided: | |

BaseSet -- All the operations common to both mutable and immutable | |

sets. This is an abstract class, not meant to be directly | |

instantiated. | |

Set -- Mutable sets, subclass of BaseSet; not hashable. | |

ImmutableSet -- Immutable sets, subclass of BaseSet; hashable. | |

An iterable argument is mandatory to create an ImmutableSet. | |

_TemporarilyImmutableSet -- A wrapper around a Set, hashable, | |

giving the same hash value as the immutable set equivalent | |

would have. Do not use this class directly. | |

Only hashable objects can be added to a Set. In particular, you cannot | |

really add a Set as an element to another Set; if you try, what is | |

actually added is an ImmutableSet built from it (it compares equal to | |

the one you tried adding). | |

When you ask if `x in y' where x is a Set and y is a Set or | |

ImmutableSet, x is wrapped into a _TemporarilyImmutableSet z, and | |

what's tested is actually `z in y'. | |

""" | |

# Code history: | |

# | |

# - Greg V. Wilson wrote the first version, using a different approach | |

# to the mutable/immutable problem, and inheriting from dict. | |

# | |

# - Alex Martelli modified Greg's version to implement the current | |

# Set/ImmutableSet approach, and make the data an attribute. | |

# | |

# - Guido van Rossum rewrote much of the code, made some API changes, | |

# and cleaned up the docstrings. | |

# | |

# - Raymond Hettinger added a number of speedups and other | |

# improvements. | |

# protect this import from the fixers... | |

exec('from itertools import ifilterfalse as filterfalse') | |

__all__ = ['BaseSet', 'Set', 'ImmutableSet'] | |

class BaseSet(object): | |

"""Common base class for mutable and immutable sets.""" | |

__slots__ = ['_data'] | |

# Constructor | |

def __init__(self): | |

"""This is an abstract class.""" | |

# Don't call this from a concrete subclass! | |

if self.__class__ is BaseSet: | |

raise TypeError("BaseSet is an abstract class. " | |

"Use Set or ImmutableSet.") | |

# Standard protocols: __len__, __repr__, __str__, __iter__ | |

def __len__(self): | |

"""Return the number of elements of a set.""" | |

return len(self._data) | |

def __repr__(self): | |

"""Return string representation of a set. | |

This looks like 'Set([<list of elements>])'. | |

""" | |

return self._repr() | |

# __str__ is the same as __repr__ | |

__str__ = __repr__ | |

def _repr(self, sort_them=False): | |

elements = list(self._data.keys()) | |

if sort_them: | |

elements.sort() | |

return '%s(%r)' % (self.__class__.__name__, elements) | |

def __iter__(self): | |

"""Return an iterator over the elements or a set. | |

This is the keys iterator for the underlying dict. | |

""" | |

# Wrapping name in () prevents fixer from "fixing" this | |

return (self._data.iterkeys)() | |

# Three-way comparison is not supported. However, because __eq__ is | |

# tried before __cmp__, if Set x == Set y, x.__eq__(y) returns True and | |

# then cmp(x, y) returns 0 (Python doesn't actually call __cmp__ in this | |

# case). | |

def __cmp__(self, other): | |

raise TypeError("can't compare sets using cmp()") | |

# Equality comparisons using the underlying dicts. Mixed-type comparisons | |

# are allowed here, where Set == z for non-Set z always returns False, | |

# and Set != z always True. This allows expressions like "x in y" to | |

# give the expected result when y is a sequence of mixed types, not | |

# raising a pointless TypeError just because y contains a Set, or x is | |

# a Set and y contain's a non-set ("in" invokes only __eq__). | |

# Subtle: it would be nicer if __eq__ and __ne__ could return | |

# NotImplemented instead of True or False. Then the other comparand | |

# would get a chance to determine the result, and if the other comparand | |

# also returned NotImplemented then it would fall back to object address | |

# comparison (which would always return False for __eq__ and always | |

# True for __ne__). However, that doesn't work, because this type | |

# *also* implements __cmp__: if, e.g., __eq__ returns NotImplemented, | |

# Python tries __cmp__ next, and the __cmp__ here then raises TypeError. | |

def __eq__(self, other): | |

if isinstance(other, BaseSet): | |

return self._data == other._data | |

else: | |

return False | |

def __ne__(self, other): | |

if isinstance(other, BaseSet): | |

return self._data != other._data | |

else: | |

return True | |

# Copying operations | |

def copy(self): | |

"""Return a shallow copy of a set.""" | |

result = self.__class__() | |

result._data.update(self._data) | |

return result | |

__copy__ = copy # For the copy module | |

def __deepcopy__(self, memo): | |

"""Return a deep copy of a set; used by copy module.""" | |

# This pre-creates the result and inserts it in the memo | |

# early, in case the deep copy recurses into another reference | |

# to this same set. A set can't be an element of itself, but | |

# it can certainly contain an object that has a reference to | |

# itself. | |

from copy import deepcopy | |

result = self.__class__() | |

memo[id(self)] = result | |

data = result._data | |

value = True | |

for elt in self: | |

data[deepcopy(elt, memo)] = value | |

return result | |

# Standard set operations: union, intersection, both differences. | |

# Each has an operator version (e.g. __or__, invoked with |) and a | |

# method version (e.g. union). | |

# Subtle: Each pair requires distinct code so that the outcome is | |

# correct when the type of other isn't suitable. For example, if | |

# we did "union = __or__" instead, then Set().union(3) would return | |

# NotImplemented instead of raising TypeError (albeit that *why* it | |

# raises TypeError as-is is also a bit subtle). | |

def __or__(self, other): | |

"""Return the union of two sets as a new set. | |

(I.e. all elements that are in either set.) | |

""" | |

if not isinstance(other, BaseSet): | |

return NotImplemented | |

return self.union(other) | |

def union(self, other): | |

"""Return the union of two sets as a new set. | |

(I.e. all elements that are in either set.) | |

""" | |

result = self.__class__(self) | |

result._update(other) | |

return result | |

def __and__(self, other): | |

"""Return the intersection of two sets as a new set. | |

(I.e. all elements that are in both sets.) | |

""" | |

if not isinstance(other, BaseSet): | |

return NotImplemented | |

return self.intersection(other) | |

def intersection(self, other): | |

"""Return the intersection of two sets as a new set. | |

(I.e. all elements that are in both sets.) | |

""" | |

if not isinstance(other, BaseSet): | |

other = Set(other) | |

if len(self) <= len(other): | |

little, big = self, other | |

else: | |

little, big = other, self | |

common = iter(filter(big._data.has_key, little)) | |

return self.__class__(common) | |

def __xor__(self, other): | |

"""Return the symmetric difference of two sets as a new set. | |

(I.e. all elements that are in exactly one of the sets.) | |

""" | |

if not isinstance(other, BaseSet): | |

return NotImplemented | |

return self.symmetric_difference(other) | |

def symmetric_difference(self, other): | |

"""Return the symmetric difference of two sets as a new set. | |

(I.e. all elements that are in exactly one of the sets.) | |

""" | |

result = self.__class__() | |

data = result._data | |

value = True | |

selfdata = self._data | |

try: | |

otherdata = other._data | |

except AttributeError: | |

otherdata = Set(other)._data | |

for elt in filterfalse(otherdata.has_key, selfdata): | |

data[elt] = value | |

for elt in filterfalse(selfdata.has_key, otherdata): | |

data[elt] = value | |

return result | |

def __sub__(self, other): | |

"""Return the difference of two sets as a new Set. | |

(I.e. all elements that are in this set and not in the other.) | |

""" | |

if not isinstance(other, BaseSet): | |

return NotImplemented | |

return self.difference(other) | |

def difference(self, other): | |

"""Return the difference of two sets as a new Set. | |

(I.e. all elements that are in this set and not in the other.) | |

""" | |

result = self.__class__() | |

data = result._data | |

try: | |

otherdata = other._data | |

except AttributeError: | |

otherdata = Set(other)._data | |

value = True | |

for elt in filterfalse(otherdata.has_key, self): | |

data[elt] = value | |

return result | |

# Membership test | |

def __contains__(self, element): | |

"""Report whether an element is a member of a set. | |

(Called in response to the expression `element in self'.) | |

""" | |

try: | |

return element in self._data | |

except TypeError: | |

transform = getattr(element, "__as_temporarily_immutable__", None) | |

if transform is None: | |

raise # re-raise the TypeError exception we caught | |

return transform() in self._data | |

# Subset and superset test | |

def issubset(self, other): | |

"""Report whether another set contains this set.""" | |

self._binary_sanity_check(other) | |

if len(self) > len(other): # Fast check for obvious cases | |

return False | |

for elt in filterfalse(other._data.has_key, self): | |

return False | |

return True | |

def issuperset(self, other): | |

"""Report whether this set contains another set.""" | |

self._binary_sanity_check(other) | |

if len(self) < len(other): # Fast check for obvious cases | |

return False | |

for elt in filterfalse(self._data.has_key, other): | |

return False | |

return True | |

# Inequality comparisons using the is-subset relation. | |

__le__ = issubset | |

__ge__ = issuperset | |

def __lt__(self, other): | |

self._binary_sanity_check(other) | |

return len(self) < len(other) and self.issubset(other) | |

def __gt__(self, other): | |

self._binary_sanity_check(other) | |

return len(self) > len(other) and self.issuperset(other) | |

# Assorted helpers | |

def _binary_sanity_check(self, other): | |

# Check that the other argument to a binary operation is also | |

# a set, raising a TypeError otherwise. | |

if not isinstance(other, BaseSet): | |

raise TypeError("Binary operation only permitted between sets") | |

def _compute_hash(self): | |

# Calculate hash code for a set by xor'ing the hash codes of | |

# the elements. This ensures that the hash code does not depend | |

# on the order in which elements are added to the set. This is | |

# not called __hash__ because a BaseSet should not be hashable; | |

# only an ImmutableSet is hashable. | |

result = 0 | |

for elt in self: | |

result ^= hash(elt) | |

return result | |

def _update(self, iterable): | |

# The main loop for update() and the subclass __init__() methods. | |

data = self._data | |

# Use the fast update() method when a dictionary is available. | |

if isinstance(iterable, BaseSet): | |

data.update(iterable._data) | |

return | |

value = True | |

if type(iterable) in (list, tuple, xrange): | |

# Optimized: we know that __iter__() and next() can't | |

# raise TypeError, so we can move 'try:' out of the loop. | |

it = iter(iterable) | |

while True: | |

try: | |

for element in it: | |

data[element] = value | |

return | |

except TypeError: | |

transform = getattr(element, "__as_immutable__", None) | |

if transform is None: | |

raise # re-raise the TypeError exception we caught | |

data[transform()] = value | |

else: | |

# Safe: only catch TypeError where intended | |

for element in iterable: | |

try: | |

data[element] = value | |

except TypeError: | |

transform = getattr(element, "__as_immutable__", None) | |

if transform is None: | |

raise # re-raise the TypeError exception we caught | |

data[transform()] = value | |

class ImmutableSet(BaseSet): | |

"""Immutable set class.""" | |

__slots__ = ['_hashcode'] | |

# BaseSet + hashing | |

def __init__(self, iterable=None): | |

"""Construct an immutable set from an optional iterable.""" | |

self._hashcode = None | |

self._data = {} | |

if iterable is not None: | |

self._update(iterable) | |

def __hash__(self): | |

if self._hashcode is None: | |

self._hashcode = self._compute_hash() | |

return self._hashcode | |

def __getstate__(self): | |

return self._data, self._hashcode | |

def __setstate__(self, state): | |

self._data, self._hashcode = state | |

class Set(BaseSet): | |

""" Mutable set class.""" | |

__slots__ = [] | |

# BaseSet + operations requiring mutability; no hashing | |

def __init__(self, iterable=None): | |

"""Construct a set from an optional iterable.""" | |

self._data = {} | |

if iterable is not None: | |

self._update(iterable) | |

def __getstate__(self): | |

# getstate's results are ignored if it is not | |

return self._data, | |

def __setstate__(self, data): | |

self._data, = data | |

def __hash__(self): | |

"""A Set cannot be hashed.""" | |

# We inherit object.__hash__, so we must deny this explicitly | |

raise TypeError("Can't hash a Set, only an ImmutableSet.") | |

# In-place union, intersection, differences. | |

# Subtle: The xyz_update() functions deliberately return None, | |

# as do all mutating operations on built-in container types. | |

# The __xyz__ spellings have to return self, though. | |

def __ior__(self, other): | |

"""Update a set with the union of itself and another.""" | |

self._binary_sanity_check(other) | |

self._data.update(other._data) | |

return self | |

def union_update(self, other): | |

"""Update a set with the union of itself and another.""" | |

self._update(other) | |

def __iand__(self, other): | |

"""Update a set with the intersection of itself and another.""" | |

self._binary_sanity_check(other) | |

self._data = (self & other)._data | |

return self | |

def intersection_update(self, other): | |

"""Update a set with the intersection of itself and another.""" | |

if isinstance(other, BaseSet): | |

self &= other | |

else: | |

self._data = (self.intersection(other))._data | |

def __ixor__(self, other): | |

"""Update a set with the symmetric difference of itself and another.""" | |

self._binary_sanity_check(other) | |

self.symmetric_difference_update(other) | |

return self | |

def symmetric_difference_update(self, other): | |

"""Update a set with the symmetric difference of itself and another.""" | |

data = self._data | |

value = True | |

if not isinstance(other, BaseSet): | |

other = Set(other) | |

if self is other: | |

self.clear() | |

for elt in other: | |

if elt in data: | |

del data[elt] | |

else: | |

data[elt] = value | |

def __isub__(self, other): | |

"""Remove all elements of another set from this set.""" | |

self._binary_sanity_check(other) | |

self.difference_update(other) | |

return self | |

def difference_update(self, other): | |

"""Remove all elements of another set from this set.""" | |

data = self._data | |

if not isinstance(other, BaseSet): | |

other = Set(other) | |

if self is other: | |

self.clear() | |

for elt in filter(data.has_key, other): | |

del data[elt] | |

# Python dict-like mass mutations: update, clear | |

def update(self, iterable): | |

"""Add all values from an iterable (such as a list or file).""" | |

self._update(iterable) | |

def clear(self): | |

"""Remove all elements from this set.""" | |

self._data.clear() | |

# Single-element mutations: add, remove, discard | |

def add(self, element): | |

"""Add an element to a set. | |

This has no effect if the element is already present. | |

""" | |

try: | |

self._data[element] = True | |

except TypeError: | |

transform = getattr(element, "__as_immutable__", None) | |

if transform is None: | |

raise # re-raise the TypeError exception we caught | |

self._data[transform()] = True | |

def remove(self, element): | |

"""Remove an element from a set; it must be a member. | |

If the element is not a member, raise a KeyError. | |

""" | |

try: | |

del self._data[element] | |

except TypeError: | |

transform = getattr(element, "__as_temporarily_immutable__", None) | |

if transform is None: | |

raise # re-raise the TypeError exception we caught | |

del self._data[transform()] | |

def discard(self, element): | |

"""Remove an element from a set if it is a member. | |

If the element is not a member, do nothing. | |

""" | |

try: | |

self.remove(element) | |

except KeyError: | |

pass | |

def pop(self): | |

"""Remove and return an arbitrary set element.""" | |

return self._data.popitem()[0] | |

def __as_immutable__(self): | |

# Return a copy of self as an immutable set | |

return ImmutableSet(self) | |

def __as_temporarily_immutable__(self): | |

# Return self wrapped in a temporarily immutable set | |

return _TemporarilyImmutableSet(self) | |

class _TemporarilyImmutableSet(BaseSet): | |

# Wrap a mutable set as if it was temporarily immutable. | |

# This only supplies hashing and equality comparisons. | |

def __init__(self, set): | |

self._set = set | |

self._data = set._data # Needed by ImmutableSet.__eq__() | |

def __hash__(self): | |

return self._set._compute_hash() | |

# Local Variables: | |

# tab-width:4 | |

# indent-tabs-mode:nil | |

# End: | |

# vim: set expandtab tabstop=4 shiftwidth=4: |