[3] | 1 | # identity.py |
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| 2 | # Copyright (C) the SQLAlchemy authors and contributors |
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| 3 | # |
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| 4 | # This module is part of SQLAlchemy and is released under |
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| 5 | # the MIT License: http://www.opensource.org/licenses/mit-license.php |
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| 6 | |
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| 7 | import weakref |
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| 8 | |
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| 9 | from sqlalchemy import util as base_util |
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| 10 | from sqlalchemy.orm import attributes |
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| 11 | |
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| 12 | |
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| 13 | class IdentityMap(dict): |
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| 14 | def __init__(self): |
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| 15 | self._mutable_attrs = set() |
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| 16 | self._modified = set() |
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| 17 | self._wr = weakref.ref(self) |
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| 18 | |
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| 19 | def replace(self, state): |
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| 20 | raise NotImplementedError() |
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| 21 | |
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| 22 | def add(self, state): |
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| 23 | raise NotImplementedError() |
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| 24 | |
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| 25 | def remove(self, state): |
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| 26 | raise NotImplementedError() |
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| 27 | |
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| 28 | def update(self, dict): |
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| 29 | raise NotImplementedError("IdentityMap uses add() to insert data") |
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| 30 | |
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| 31 | def clear(self): |
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| 32 | raise NotImplementedError("IdentityMap uses remove() to remove data") |
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| 33 | |
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| 34 | def _manage_incoming_state(self, state): |
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| 35 | state._instance_dict = self._wr |
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| 36 | |
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| 37 | if state.modified: |
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| 38 | self._modified.add(state) |
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| 39 | if state.manager.mutable_attributes: |
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| 40 | self._mutable_attrs.add(state) |
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| 41 | |
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| 42 | def _manage_removed_state(self, state): |
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| 43 | del state._instance_dict |
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| 44 | self._mutable_attrs.discard(state) |
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| 45 | self._modified.discard(state) |
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| 46 | |
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| 47 | def _dirty_states(self): |
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| 48 | return self._modified.union(s for s in list(self._mutable_attrs) |
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| 49 | if s.modified) |
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| 50 | |
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| 51 | def check_modified(self): |
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| 52 | """return True if any InstanceStates present have been marked as 'modified'.""" |
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| 53 | |
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| 54 | if self._modified: |
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| 55 | return True |
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| 56 | else: |
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| 57 | for state in list(self._mutable_attrs): |
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| 58 | if state.modified: |
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| 59 | return True |
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| 60 | return False |
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| 61 | |
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| 62 | def has_key(self, key): |
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| 63 | return key in self |
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| 64 | |
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| 65 | def popitem(self): |
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| 66 | raise NotImplementedError("IdentityMap uses remove() to remove data") |
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| 67 | |
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| 68 | def pop(self, key, *args): |
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| 69 | raise NotImplementedError("IdentityMap uses remove() to remove data") |
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| 70 | |
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| 71 | def setdefault(self, key, default=None): |
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| 72 | raise NotImplementedError("IdentityMap uses add() to insert data") |
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| 73 | |
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| 74 | def copy(self): |
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| 75 | raise NotImplementedError() |
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| 76 | |
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| 77 | def __setitem__(self, key, value): |
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| 78 | raise NotImplementedError("IdentityMap uses add() to insert data") |
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| 79 | |
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| 80 | def __delitem__(self, key): |
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| 81 | raise NotImplementedError("IdentityMap uses remove() to remove data") |
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| 82 | |
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| 83 | class WeakInstanceDict(IdentityMap): |
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| 84 | |
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| 85 | def __getitem__(self, key): |
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| 86 | state = dict.__getitem__(self, key) |
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| 87 | o = state.obj() |
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| 88 | if o is None: |
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| 89 | o = state._is_really_none() |
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| 90 | if o is None: |
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| 91 | raise KeyError, key |
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| 92 | return o |
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| 93 | |
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| 94 | def __contains__(self, key): |
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| 95 | try: |
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| 96 | if dict.__contains__(self, key): |
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| 97 | state = dict.__getitem__(self, key) |
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| 98 | o = state.obj() |
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| 99 | if o is None: |
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| 100 | o = state._is_really_none() |
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| 101 | else: |
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| 102 | return False |
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| 103 | except KeyError: |
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| 104 | return False |
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| 105 | return o is not None |
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| 106 | |
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| 107 | def contains_state(self, state): |
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| 108 | return dict.get(self, state.key) is state |
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| 109 | |
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| 110 | def replace(self, state): |
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| 111 | if dict.__contains__(self, state.key): |
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| 112 | existing = dict.__getitem__(self, state.key) |
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| 113 | if existing is not state: |
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| 114 | self._manage_removed_state(existing) |
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| 115 | else: |
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| 116 | return |
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| 117 | |
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| 118 | dict.__setitem__(self, state.key, state) |
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| 119 | self._manage_incoming_state(state) |
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| 120 | |
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| 121 | def add(self, state): |
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| 122 | if state.key in self: |
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| 123 | if dict.__getitem__(self, state.key) is not state: |
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| 124 | raise AssertionError("A conflicting state is already present in the identity map for key %r" % (state.key, )) |
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| 125 | else: |
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| 126 | dict.__setitem__(self, state.key, state) |
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| 127 | self._manage_incoming_state(state) |
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| 128 | |
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| 129 | def remove_key(self, key): |
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| 130 | state = dict.__getitem__(self, key) |
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| 131 | self.remove(state) |
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| 132 | |
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| 133 | def remove(self, state): |
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| 134 | if dict.pop(self, state.key) is not state: |
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| 135 | raise AssertionError("State %s is not present in this identity map" % state) |
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| 136 | self._manage_removed_state(state) |
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| 137 | |
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| 138 | def discard(self, state): |
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| 139 | if self.contains_state(state): |
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| 140 | dict.__delitem__(self, state.key) |
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| 141 | self._manage_removed_state(state) |
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| 142 | |
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| 143 | def get(self, key, default=None): |
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| 144 | try: |
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| 145 | return self[key] |
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| 146 | except KeyError: |
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| 147 | return default |
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| 148 | |
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| 149 | def items(self): |
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| 150 | return list(self.iteritems()) |
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| 151 | |
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| 152 | def iteritems(self): |
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| 153 | for state in dict.itervalues(self): |
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| 154 | value = state.obj() |
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| 155 | if value is not None: |
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| 156 | yield state.key, value |
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| 157 | |
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| 158 | def itervalues(self): |
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| 159 | for state in dict.itervalues(self): |
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| 160 | instance = state.obj() |
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| 161 | if instance is not None: |
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| 162 | yield instance |
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| 163 | |
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| 164 | def values(self): |
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| 165 | return list(self.itervalues()) |
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| 166 | |
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| 167 | def all_states(self): |
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| 168 | return dict.values(self) |
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| 169 | |
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| 170 | def prune(self): |
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| 171 | return 0 |
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| 172 | |
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| 173 | class StrongInstanceDict(IdentityMap): |
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| 174 | def all_states(self): |
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| 175 | return [attributes.instance_state(o) for o in self.values()] |
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| 176 | |
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| 177 | def contains_state(self, state): |
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| 178 | return state.key in self and attributes.instance_state(self[state.key]) is state |
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| 179 | |
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| 180 | def replace(self, state): |
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| 181 | if dict.__contains__(self, state.key): |
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| 182 | existing = dict.__getitem__(self, state.key) |
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| 183 | existing = attributes.instance_state(existing) |
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| 184 | if existing is not state: |
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| 185 | self._manage_removed_state(existing) |
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| 186 | else: |
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| 187 | return |
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| 188 | |
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| 189 | dict.__setitem__(self, state.key, state.obj()) |
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| 190 | self._manage_incoming_state(state) |
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| 191 | |
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| 192 | def add(self, state): |
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| 193 | if state.key in self: |
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| 194 | if attributes.instance_state(dict.__getitem__(self, state.key)) is not state: |
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| 195 | raise AssertionError("A conflicting state is already present in the identity map for key %r" % (state.key, )) |
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| 196 | else: |
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| 197 | dict.__setitem__(self, state.key, state.obj()) |
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| 198 | self._manage_incoming_state(state) |
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| 199 | |
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| 200 | def remove(self, state): |
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| 201 | if attributes.instance_state(dict.pop(self, state.key)) is not state: |
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| 202 | raise AssertionError("State %s is not present in this identity map" % state) |
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| 203 | self._manage_removed_state(state) |
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| 204 | |
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| 205 | def discard(self, state): |
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| 206 | if self.contains_state(state): |
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| 207 | dict.__delitem__(self, state.key) |
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| 208 | self._manage_removed_state(state) |
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| 209 | |
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| 210 | def remove_key(self, key): |
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| 211 | state = attributes.instance_state(dict.__getitem__(self, key)) |
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| 212 | self.remove(state) |
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| 213 | |
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| 214 | def prune(self): |
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| 215 | """prune unreferenced, non-dirty states.""" |
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| 216 | |
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| 217 | ref_count = len(self) |
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| 218 | dirty = [s.obj() for s in self.all_states() if s.check_modified()] |
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| 219 | keepers = weakref.WeakValueDictionary(self) |
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| 220 | dict.clear(self) |
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| 221 | dict.update(self, keepers) |
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| 222 | self.modified = bool(dirty) |
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| 223 | return ref_count - len(self) |
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| 224 | |
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