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1 """Python version compatibility support for minidom.
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2
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3 This module contains internal implementation details and
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4 should not be imported; use xml.dom.minidom instead.
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5 """
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6
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7 # This module should only be imported using "import *".
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8 #
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9 # The following names are defined:
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10 #
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11 # NodeList -- lightest possible NodeList implementation
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12 #
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13 # EmptyNodeList -- lightest possible NodeList that is guaranteed to
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14 # remain empty (immutable)
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15 #
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16 # StringTypes -- tuple of defined string types
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17 #
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18 # defproperty -- function used in conjunction with GetattrMagic;
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19 # using these together is needed to make them work
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20 # as efficiently as possible in both Python 2.2+
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21 # and older versions. For example:
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22 #
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23 # class MyClass(GetattrMagic):
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24 # def _get_myattr(self):
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25 # return something
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26 #
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27 # defproperty(MyClass, "myattr",
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28 # "return some value")
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29 #
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30 # For Python 2.2 and newer, this will construct a
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31 # property object on the class, which avoids
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32 # needing to override __getattr__(). It will only
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33 # work for read-only attributes.
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34 #
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35 # For older versions of Python, inheriting from
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36 # GetattrMagic will use the traditional
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37 # __getattr__() hackery to achieve the same effect,
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38 # but less efficiently.
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39 #
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40 # defproperty() should be used for each version of
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41 # the relevant _get_<property>() function.
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42
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43 __all__ = ["NodeList", "EmptyNodeList", "StringTypes", "defproperty"]
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44
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45 import xml.dom
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46
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47 StringTypes = (str,)
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48
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49
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50 class NodeList(list):
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51 __slots__ = ()
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52
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53 def item(self, index):
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54 if 0 <= index < len(self):
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55 return self[index]
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56
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57 def _get_length(self):
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58 return len(self)
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59
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60 def _set_length(self, value):
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61 raise xml.dom.NoModificationAllowedErr(
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62 "attempt to modify read-only attribute 'length'")
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63
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64 length = property(_get_length, _set_length,
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65 doc="The number of nodes in the NodeList.")
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66
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67 # For backward compatibility
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68 def __setstate__(self, state):
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69 if state is None:
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70 state = []
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71 self[:] = state
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72
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73
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74 class EmptyNodeList(tuple):
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75 __slots__ = ()
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76
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77 def __add__(self, other):
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78 NL = NodeList()
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79 NL.extend(other)
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80 return NL
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81
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82 def __radd__(self, other):
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83 NL = NodeList()
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84 NL.extend(other)
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85 return NL
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86
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87 def item(self, index):
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88 return None
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89
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90 def _get_length(self):
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91 return 0
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92
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93 def _set_length(self, value):
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94 raise xml.dom.NoModificationAllowedErr(
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95 "attempt to modify read-only attribute 'length'")
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96
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97 length = property(_get_length, _set_length,
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98 doc="The number of nodes in the NodeList.")
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99
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100
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101 def defproperty(klass, name, doc):
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102 get = getattr(klass, ("_get_" + name))
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103 def set(self, value, name=name):
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104 raise xml.dom.NoModificationAllowedErr(
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105 "attempt to modify read-only attribute " + repr(name))
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106 assert not hasattr(klass, "_set_" + name), \
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107 "expected not to find _set_" + name
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108 prop = property(get, set, doc=doc)
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109 setattr(klass, name, prop)
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