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import math
import struct
HUGEVAL_BYTES = struct.calcsize('P')
HUGEVAL = 256 ** HUGEVAL_BYTES
def fixid(result):
if result < 0:
result += HUGEVAL
return result
uid = id # guaranteed to be positive from CPython 2.5 onwards
class Hashable(object):
"""
A Hashable instance encapsulates any object, but is always usable as a
key in dictionaries. This is based on id() for mutable objects and on
real hash/compare for immutable ones.
"""
__slots__ = ["key", "value"]
def __init__(self, value):
self.value = value # a concrete value
# try to be smart about constant mutable or immutable values
key = type(self.value), self.value # to avoid confusing e.g. 0 and 0.0
#
# we also have to avoid confusing 0.0 and -0.0 (needed e.g. for
# translating the cmath module)
if key[0] is float and not self.value:
if math.copysign(1., self.value) == -1.: # -0.0
key = (float, "-0.0")
#
try:
hash(key)
except TypeError:
key = id(self.value)
self.key = key
def __eq__(self, other):
return self.__class__ is other.__class__ and self.key == other.key
def __ne__(self, other):
return not (self == other)
def __hash__(self):
return hash(self.key)
def __repr__(self):
return '(%s)' % (self,)
def __str__(self):
# try to limit the size of the repr to make it more readable
r = repr(self.value)
if (r.startswith('<') and r.endswith('>') and
hasattr(self.value, '__name__')):
r = '%s %s' % (type(self.value).__name__, self.value.__name__)
elif len(r) > 60 or (len(r) > 30 and type(self.value) is not str):
r = r[:22] + '...' + r[-7:]
return r
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