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# Licensed under a 3-clause BSD style license - see LICENSE.rst
"""
A module containing specialized collection classes.
"""
class HomogeneousList(list):
"""
A subclass of list that contains only elements of a given type or
types. If an item that is not of the specified type is added to
the list, a `TypeError` is raised.
"""
def __init__(self, types, values=[]):
"""
Parameters
----------
types : sequence of types
The types to accept.
values : sequence, optional
An initial set of values.
"""
self._types = types
list.__init__(self, values)
def _assert(self, x):
if not isinstance(x, self._types):
raise TypeError(
"homogeneous list must contain only objects of "
"type '{}'".format(self._types))
def __iadd__(self, other):
for x in other:
self._assert(x)
return list.__iadd__(self, other)
def __setitem__(self, x):
self._assert(x)
return list.__setitem__(self, x)
def append(self, x):
self._assert(x)
return list.append(self, x)
def insert(self, i, x):
self._assert(x)
return list.insert(self, i, x)
def extend(self, x):
for item in x:
self._assert(item)
return list.extend(self, x)
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