Mercurial > cpython-lru_cache-weakref

annotate Lib/copy.py @ 4566:6403c94de50d legacy-trunk

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Added safeguard against failure in __del__.
author Guido van Rossum <guido@python.org>
date Wed, 27 Nov 1996 19:39:58 +0000
parents a1362a063122
children 6f9a2c874018
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1 """\
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2 Generic (shallow and deep) copying operations
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3 =============================================
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4
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5 Interface summary:
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6
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7 import copy
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8
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9 x = copy.copy(y) # make a shallow copy of y
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10 x = copy.deepcopy(y) # make a deep copy of y
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11
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12 For module specific errors, copy.error is raised.
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13
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14 The difference between shallow and deep copying is only relevant for
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15 compound objects (objects that contain other objects, like lists or
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16 class instances).
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17
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18 - A shallow copy constructs a new compound object and then (to the
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19 extent possible) inserts *the same objects* into in that the
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20 original contains.
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21
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22 - A deep copy constructs a new compound object and then, recursively,
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23 inserts *copies* into it of the objects found in the original.
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24
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25 Two problems often exist with deep copy operations that don't exist
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26 with shallow copy operations:
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27
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28 (a) recursive objects (compound objects that, directly or indirectly,
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29 contain a reference to themselves) may cause a recursive loop
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30
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31 (b) because deep copy copies *everything* it may copy too much, e.g.
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32 administrative data structures that should be shared even between
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33 copies
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34
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35 Python's deep copy operation avoids these problems by:
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36
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37 (a) keeping a table of objects already copied during the current
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38 copying pass
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39
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40 (b) letting user-defined classes override the copying operation or the
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41 set of components copied
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42
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43 This version does not copy types like module, class, function, method,
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44 nor stack trace, stack frame, nor file, socket, window, nor array, nor
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45 any similar types.
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46
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47 Classes can use the same interfaces to control copying that they use
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48 to control pickling: they can define methods called __getinitargs__(),
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49 __getstate__() and __setstate__(). See the __doc__ string of module
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50 "pickle" for information on these methods.
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51 """
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52
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53 import types
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54
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55 error = 'copy.error'
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56 Error = error # backward compatibility
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57
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58 def copy(x):
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59 """Shallow copy operation on arbitrary Python objects.
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60
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61 See the module's __doc__ string for more info.
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62 """
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63
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64 try:
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65 copierfunction = _copy_dispatch[type(x)]
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66 except KeyError:
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67 try:
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68 copier = x.__copy__
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69 except AttributeError:
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70 raise error, \
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71 "un(shallow)copyable object of type %s" % type(x)
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72 y = copier()
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73 else:
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74 y = copierfunction(x)
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75 return y
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76
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77 _copy_dispatch = d = {}
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78
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79 def _copy_atomic(x):
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80 return x
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81 d[types.NoneType] = _copy_atomic
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82 d[types.IntType] = _copy_atomic
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83 d[types.LongType] = _copy_atomic
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84 d[types.FloatType] = _copy_atomic
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85 d[types.StringType] = _copy_atomic
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86 d[types.CodeType] = _copy_atomic
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87 d[types.TypeType] = _copy_atomic
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88 d[types.XRangeType] = _copy_atomic
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89 d[types.ClassType] = _copy_atomic
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90
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91 def _copy_list(x):
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92 return x[:]
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93 d[types.ListType] = _copy_list
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94
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95 def _copy_tuple(x):
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96 return x[:]
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97 d[types.TupleType] = _copy_tuple
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98
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99 def _copy_dict(x):
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100 y = {}
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101 for key in x.keys():
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102 y[key] = x[key]
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103 return y
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104 d[types.DictionaryType] = _copy_dict
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105
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106 def _copy_inst(x):
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107 if hasattr(x, '__copy__'):
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108 return x.__copy__()
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109 if hasattr(x, '__getinitargs__'):
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110 args = x.__getinitargs__()
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111 else:
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112 args = ()
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113 y = apply(x.__class__, args)
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114 if hasattr(x, '__getstate__'):
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115 state = x.__getstate__()
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116 else:
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117 state = x.__dict__
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118 if hasattr(y, '__setstate__'):
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119 y.__setstate__(state)
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120 else:
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121 for key in state.keys():
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122 setattr(y, key, state[key])
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123 return y
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124 d[types.InstanceType] = _copy_inst
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125
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126 del d
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127
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128 def deepcopy(x, memo = None):
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129 """Deep copy operation on arbitrary Python objects.
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130
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131 See the module's __doc__ string for more info.
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132 """
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133
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134 if memo is None:
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135 memo = {}
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136 d = id(x)
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137 if memo.has_key(d):
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138 return memo[d]
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139 try:
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140 copierfunction = _deepcopy_dispatch[type(x)]
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141 except KeyError:
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142 try:
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143 copier = x.__deepcopy__
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144 except AttributeError:
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145 raise error, \
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146 "un-deep-copyable object of type %s" % type(x)
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147 y = copier(memo)
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148 else:
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149 y = copierfunction(x, memo)
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150 memo[d] = y
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151 return y
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152
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153 _deepcopy_dispatch = d = {}
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154
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155 def _deepcopy_atomic(x, memo):
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156 return x
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157 d[types.NoneType] = _deepcopy_atomic
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158 d[types.IntType] = _deepcopy_atomic
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159 d[types.LongType] = _deepcopy_atomic
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160 d[types.FloatType] = _deepcopy_atomic
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161 d[types.StringType] = _deepcopy_atomic
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162 d[types.CodeType] = _deepcopy_atomic
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163 d[types.TypeType] = _deepcopy_atomic
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164 d[types.XRangeType] = _deepcopy_atomic
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165
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166 def _deepcopy_list(x, memo):
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167 y = []
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168 memo[id(x)] = y
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169 for a in x:
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170 y.append(deepcopy(a, memo))
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171 return y
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172 d[types.ListType] = _deepcopy_list
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173
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174 def _deepcopy_tuple(x, memo):
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175 y = []
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176 for a in x:
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177 y.append(deepcopy(a, memo))
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178 d = id(x)
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179 try:
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180 return memo[d]
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181 except KeyError:
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182 pass
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183 for i in range(len(x)):
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184 if x[i] is not y[i]:
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a1362a063122 Memoize _deepcopy_tuple() -- maybe this helps Tommy's problem.
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185 y = tuple(y)
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186 break
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187 else:
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188 y = x
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189 memo[d] = y
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190 return y
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191 d[types.TupleType] = _deepcopy_tuple
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192
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193 def _deepcopy_dict(x, memo):
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194 y = {}
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195 memo[id(x)] = y
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196 for key in x.keys():
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197 y[deepcopy(key, memo)] = deepcopy(x[key], memo)
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198 return y
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199 d[types.DictionaryType] = _deepcopy_dict
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200
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201 def _deepcopy_inst(x, memo):
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202 if hasattr(x, '__deepcopy__'):
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203 return x.__deepcopy__()
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204 if hasattr(x, '__getinitargs__'):
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205 args = x.__getinitargs__()
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206 args = deepcopy(args, memo)
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207 else:
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208 args = ()
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209 y = apply(x.__class__, args)
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210 memo[id(x)] = y
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211 if hasattr(x, '__getstate__'):
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212 state = x.__getstate__()
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213 else:
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214 state = x.__dict__
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215 state = deepcopy(state, memo)
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216 if hasattr(y, '__setstate__'):
2101
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217 y.__setstate__(state)
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218 else:
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219 for key in state.keys():
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220 setattr(y, key, state[key])
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221 return y
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222 d[types.InstanceType] = _deepcopy_inst
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223
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224 del d
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225
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226 del types
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227
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228 def _test():
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d7ae5fb1d255 rename copy.Error to copy.error
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229 l = [None, 1, 2L, 3.14, 'xyzzy', (1, 2L), [3.14, 'abc'],
d7ae5fb1d255 rename copy.Error to copy.error
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230 {'abc': 'ABC'}, (), [], {}]
2101
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231 l1 = copy(l)
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232 print l1==l
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233 l1 = map(copy, l)
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234 print l1==l
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235 l1 = deepcopy(l)
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236 print l1==l
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237 class C:
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238 def __init__(self, arg=None):
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239 self.a = 1
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240 self.arg = arg
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241 self.fp = open('copy.py')
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242 self.fp.close()
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243 def __getstate__(self):
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244 return {'a': self.a, 'arg': self.arg}
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245 def __setstate__(self, state):
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246 for key in state.keys():
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247 setattr(self, key, state[key])
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248 def __deepcopy__(self, memo = None):
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249 new = self.__class__(deepcopy(self.arg, memo))
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250 new.a = self.a
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251 return new
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252 c = C('argument sketch')
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253 l.append(c)
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254 l2 = copy(l)
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255 print l == l2
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256 print l
fdccc3222d0a shallow and deep copy operations
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257 print l2
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258 l2 = deepcopy(l)
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259 print l == l2
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260 print l
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261 print l2
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262 l.append({l[1]: l, 'xyz': l[2]})
fdccc3222d0a shallow and deep copy operations
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263 l3 = copy(l)
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264 import repr
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265 print map(repr.repr, l)
fdccc3222d0a shallow and deep copy operations
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266 print map(repr.repr, l1)
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267 print map(repr.repr, l2)
fdccc3222d0a shallow and deep copy operations
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268 print map(repr.repr, l3)
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269 l3 = deepcopy(l)
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270 import repr
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271 print map(repr.repr, l)
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272 print map(repr.repr, l1)
fdccc3222d0a shallow and deep copy operations
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273 print map(repr.repr, l2)
fdccc3222d0a shallow and deep copy operations
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274 print map(repr.repr, l3)
fdccc3222d0a shallow and deep copy operations
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275
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276 if __name__ == '__main__':
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277 _test()