Mercurial > cpython-lru_cache-weakref

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Add use_weakref option to functools.lru_cache The use_weakref option makes lru_cache create weak references to the function arguments when creating the cache key, which prevents them from staying in the memory forever even after all other references to them are gone. This is a proof of concept for http://bugs.python.org/issue19859
author Radomir Dopieralski <devel@sheep.art.pl>
date Tue, 03 Dec 2013 16:02:48 +0100
parents 5b17d5ca2ff1
children
Ignore whitespace changes - Everywhere: Within whitespace: At end of lines:
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1 # Copyright 2007 Google, Inc. All Rights Reserved.
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2 # Licensed to PSF under a Contributor Agreement.
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3
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4 """Abstract Base Classes (ABCs) according to PEP 3119."""
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5
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6 from _weakrefset import WeakSet
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7
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8
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9 def abstractmethod(funcobj):
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10 """A decorator indicating abstract methods.
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11
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12 Requires that the metaclass is ABCMeta or derived from it. A
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13 class that has a metaclass derived from ABCMeta cannot be
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14 instantiated unless all of its abstract methods are overridden.
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15 The abstract methods can be called using any of the normal
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16 'super' call mechanisms.
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17
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18 Usage:
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19
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20 class C(metaclass=ABCMeta):
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21 @abstractmethod
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22 def my_abstract_method(self, ...):
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23 ...
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24 """
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25 funcobj.__isabstractmethod__ = True
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26 return funcobj
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27
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28
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29 class abstractclassmethod(classmethod):
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30 """
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31 A decorator indicating abstract classmethods.
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32
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33 Similar to abstractmethod.
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34
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35 Usage:
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36
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37 class C(metaclass=ABCMeta):
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38 @abstractclassmethod
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39 def my_abstract_classmethod(cls, ...):
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40 ...
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41
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42 'abstractclassmethod' is deprecated. Use 'classmethod' with
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43 'abstractmethod' instead.
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44 """
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45
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46 __isabstractmethod__ = True
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47
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48 def __init__(self, callable):
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49 callable.__isabstractmethod__ = True
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50 super().__init__(callable)
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51
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52
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53 class abstractstaticmethod(staticmethod):
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54 """
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55 A decorator indicating abstract staticmethods.
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56
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57 Similar to abstractmethod.
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58
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59 Usage:
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60
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61 class C(metaclass=ABCMeta):
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62 @abstractstaticmethod
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63 def my_abstract_staticmethod(...):
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64 ...
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65
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66 'abstractstaticmethod' is deprecated. Use 'staticmethod' with
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67 'abstractmethod' instead.
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68 """
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69
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70 __isabstractmethod__ = True
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71
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72 def __init__(self, callable):
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73 callable.__isabstractmethod__ = True
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74 super().__init__(callable)
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75
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76
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77 class abstractproperty(property):
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78 """
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79 A decorator indicating abstract properties.
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80
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81 Requires that the metaclass is ABCMeta or derived from it. A
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82 class that has a metaclass derived from ABCMeta cannot be
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83 instantiated unless all of its abstract properties are overridden.
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84 The abstract properties can be called using any of the normal
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85 'super' call mechanisms.
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86
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87 Usage:
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88
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89 class C(metaclass=ABCMeta):
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90 @abstractproperty
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91 def my_abstract_property(self):
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92 ...
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93
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94 This defines a read-only property; you can also define a read-write
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95 abstract property using the 'long' form of property declaration:
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96
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97 class C(metaclass=ABCMeta):
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98 def getx(self): ...
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99 def setx(self, value): ...
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100 x = abstractproperty(getx, setx)
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101
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102 'abstractproperty' is deprecated. Use 'property' with 'abstractmethod'
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103 instead.
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104 """
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105
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106 __isabstractmethod__ = True
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107
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108
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109 class ABCMeta(type):
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110
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111 """Metaclass for defining Abstract Base Classes (ABCs).
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112
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113 Use this metaclass to create an ABC. An ABC can be subclassed
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114 directly, and then acts as a mix-in class. You can also register
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115 unrelated concrete classes (even built-in classes) and unrelated
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116 ABCs as 'virtual subclasses' -- these and their descendants will
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117 be considered subclasses of the registering ABC by the built-in
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118 issubclass() function, but the registering ABC won't show up in
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119 their MRO (Method Resolution Order) nor will method
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120 implementations defined by the registering ABC be callable (not
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121 even via super()).
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122
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123 """
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124
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125 # A global counter that is incremented each time a class is
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126 # registered as a virtual subclass of anything. It forces the
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127 # negative cache to be cleared before its next use.
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128 # Note: this counter is private. Use `abc.get_cache_token()` for
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129 # external code.
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130 _abc_invalidation_counter = 0
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131
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132 def __new__(mcls, name, bases, namespace):
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133 cls = super().__new__(mcls, name, bases, namespace)
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134 # Compute set of abstract method names
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135 abstracts = {name
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136 for name, value in namespace.items()
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137 if getattr(value, "__isabstractmethod__", False)}
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138 for base in bases:
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139 for name in getattr(base, "__abstractmethods__", set()):
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140 value = getattr(cls, name, None)
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141 if getattr(value, "__isabstractmethod__", False):
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142 abstracts.add(name)
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143 cls.__abstractmethods__ = frozenset(abstracts)
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144 # Set up inheritance registry
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145 cls._abc_registry = WeakSet()
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146 cls._abc_cache = WeakSet()
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147 cls._abc_negative_cache = WeakSet()
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148 cls._abc_negative_cache_version = ABCMeta._abc_invalidation_counter
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149 return cls
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150
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151 def register(cls, subclass):
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152 """Register a virtual subclass of an ABC.
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153
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154 Returns the subclass, to allow usage as a class decorator.
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155 """
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156 if not isinstance(subclass, type):
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157 raise TypeError("Can only register classes")
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158 if issubclass(subclass, cls):
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159 return subclass # Already a subclass
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160 # Subtle: test for cycles *after* testing for "already a subclass";
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161 # this means we allow X.register(X) and interpret it as a no-op.
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162 if issubclass(cls, subclass):
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163 # This would create a cycle, which is bad for the algorithm below
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164 raise RuntimeError("Refusing to create an inheritance cycle")
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165 cls._abc_registry.add(subclass)
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166 ABCMeta._abc_invalidation_counter += 1 # Invalidate negative cache
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167 return subclass
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168
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169 def _dump_registry(cls, file=None):
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170 """Debug helper to print the ABC registry."""
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171 print("Class: %s.%s" % (cls.__module__, cls.__name__), file=file)
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172 print("Inv.counter: %s" % ABCMeta._abc_invalidation_counter, file=file)
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173 for name in sorted(cls.__dict__.keys()):
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174 if name.startswith("_abc_"):
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175 value = getattr(cls, name)
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176 print("%s: %r" % (name, value), file=file)
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177
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178 def __instancecheck__(cls, instance):
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179 """Override for isinstance(instance, cls)."""
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180 # Inline the cache checking
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181 subclass = instance.__class__
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182 if subclass in cls._abc_cache:
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183 return True
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184 subtype = type(instance)
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185 if subtype is subclass:
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186 if (cls._abc_negative_cache_version ==
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187 ABCMeta._abc_invalidation_counter and
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188 subclass in cls._abc_negative_cache):
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189 return False
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190 # Fall back to the subclass check.
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191 return cls.__subclasscheck__(subclass)
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192 return any(cls.__subclasscheck__(c) for c in {subclass, subtype})
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193
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194 def __subclasscheck__(cls, subclass):
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195 """Override for issubclass(subclass, cls)."""
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196 # Check cache
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197 if subclass in cls._abc_cache:
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198 return True
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199 # Check negative cache; may have to invalidate
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200 if cls._abc_negative_cache_version < ABCMeta._abc_invalidation_counter:
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201 # Invalidate the negative cache
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202 cls._abc_negative_cache = WeakSet()
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203 cls._abc_negative_cache_version = ABCMeta._abc_invalidation_counter
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204 elif subclass in cls._abc_negative_cache:
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205 return False
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206 # Check the subclass hook
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207 ok = cls.__subclasshook__(subclass)
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208 if ok is not NotImplemented:
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209 assert isinstance(ok, bool)
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210 if ok:
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211 cls._abc_cache.add(subclass)
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212 else:
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213 cls._abc_negative_cache.add(subclass)
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214 return ok
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215 # Check if it's a direct subclass
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216 if cls in getattr(subclass, '__mro__', ()):
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217 cls._abc_cache.add(subclass)
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218 return True
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219 # Check if it's a subclass of a registered class (recursive)
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220 for rcls in cls._abc_registry:
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221 if issubclass(subclass, rcls):
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222 cls._abc_cache.add(subclass)
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223 return True
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224 # Check if it's a subclass of a subclass (recursive)
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225 for scls in cls.__subclasses__():
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226 if issubclass(subclass, scls):
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Nick Coghlan <ncoghlan@gmail.com>
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227 cls._abc_cache.add(subclass)
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228 return True
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229 # No dice; update negative cache
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2f4679301132 Rename __whatever variables defined by ABCMeta to _abc_whatever, so as
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230 cls._abc_negative_cache.add(subclass)
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231 return False
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Andrew Svetlov <andrew.svetlov@gmail.com>
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232
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233
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234 class ABC(metaclass=ABCMeta):
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235 """Helper class that provides a standard way to create an ABC using
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236 inheritance.
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237 """
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238 pass
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239
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240
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Łukasz Langa <lukasz@langa.pl>
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241 def get_cache_token():
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242 """Returns the current ABC cache token.
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243
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244 The token is an opaque integer identifying the current version of
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245 the ABC cache for virtual subclasses. This number changes with
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246 every call to ``register()`` on any ABC.
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247 """
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248 return ABCMeta._abc_invalidation_counter