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"""Class definition for bijection."""
from collections.abc import Mapping, MutableMapping
__all__ = ('bijection', )
class bijection(MutableMapping):
"""A one-to-one onto mapping, a dict with unique values."""
def __init__(self, iterable=None, **kwarg):
"""Create a bijection from an iterable.
Matches dict.__init__.
"""
self._data = {}
self.__inverse = self.__new__(bijection)
self.__inverse._data = {}
self.__inverse.__inverse = self
if iterable is not None:
if isinstance(iterable, Mapping):
for key, value in iterable.items():
self[key] = value
else:
for pair in iterable:
key, value = pair
self[key] = value
for key, value in kwarg.items():
self[key] = value
def __repr__(self):
if len(self._data) == 0:
return '{0}()'.format(self.__class__.__name__)
else:
repr_format = '{class_name}({values!r})'
return repr_format.format(
class_name=self.__class__.__name__,
values=self._data,
)
@property
def inverse(self):
"""Return the inverse of this bijection."""
return self.__inverse
# Required for MutableMapping
def __len__(self):
return len(self._data)
# Required for MutableMapping
def __getitem__(self, key):
return self._data[key]
# Required for MutableMapping
def __setitem__(self, key, value):
if key in self:
del self.inverse._data[self[key]]
if value in self.inverse:
del self._data[self.inverse[value]]
self._data[key] = value
self.inverse._data[value] = key
# Required for MutableMapping
def __delitem__(self, key):
value = self._data.pop(key)
del self.inverse._data[value]
# Required for MutableMapping
def __iter__(self):
return iter(self._data)
def __contains__(self, key):
return key in self._data
def clear(self):
"""Remove everything from this bijection."""
self._data.clear()
self.inverse._data.clear()
def copy(self):
"""Return a copy of this bijection."""
return bijection(self)
def items(self):
"""See Mapping.items."""
return self._data.items()
def keys(self):
"""See Mapping.keys."""
return self._data.keys()
def values(self):
"""See Mapping.values."""
return self.inverse.keys()
def __eq__(self, other):
return isinstance(other, bijection) and self._data == other._data
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