1
# Copyright (C) 2009 Canonical Ltd
3
# This program is free software; you can redistribute it and/or modify
4
# it under the terms of the GNU General Public License as published by
5
# the Free Software Foundation; either version 2 of the License, or
6
# (at your option) any later version.
8
# This program is distributed in the hope that it will be useful,
9
# but WITHOUT ANY WARRANTY; without even the implied warranty of
10
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
11
# GNU General Public License for more details.
13
# You should have received a copy of the GNU General Public License
14
# along with this program; if not, write to the Free Software
15
# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
17
"""The pure-python implementation of the StaticTuple type.
19
Note that it is generally just implemented as using tuples of tuples of
24
class StaticTuple(tuple):
25
"""A static type, similar to a tuple of strings."""
27
def __new__(cls, *args):
28
# Make the empty StaticTuple a singleton
29
if not args and _empty_tuple is not None:
31
return tuple.__new__(cls, args)
33
def __init__(self, *args):
34
"""Create a new 'StaticTuple'"""
36
if type(bit) not in (str, StaticTuple):
37
raise TypeError('key bits must be strings or StaticTuple')
39
if num_keys < 0 or num_keys > 255:
40
raise ValueError('must have 1 => 256 key bits')
41
# We don't need to pass args to tuple.__init__, because that was
42
# already handled in __new__.
46
return '%s%s' % (self.__class__.__name__, tuple.__repr__(self))
52
return _interned_tuples.setdefault(self, self)
55
# Have to set it to None first, so that __new__ can determine whether
56
# the _empty_tuple singleton has been created yet or not.
58
_empty_tuple = StaticTuple()