1 """Python version compatibility support for minidom."""

     2 

     3 # This module should only be imported using "import *".

     4 #

     5 # The following names are defined:

     6 #

     7 #   NodeList      -- lightest possible NodeList implementation

     8 #

     9 #   EmptyNodeList -- lightest possible NodeList that is guarateed to

    10 #                    remain empty (immutable)

    11 #

    12 #   StringTypes   -- tuple of defined string types

    13 #

    14 #   defproperty   -- function used in conjunction with GetattrMagic;

    15 #                    using these together is needed to make them work

    16 #                    as efficiently as possible in both Python 2.2+

    17 #                    and older versions.  For example:

    18 #

    19 #                        class MyClass(GetattrMagic):

    20 #                            def _get_myattr(self):

    21 #                                return something

    22 #

    23 #                        defproperty(MyClass, "myattr",

    24 #                                    "return some value")

    25 #

    26 #                    For Python 2.2 and newer, this will construct a

    27 #                    property object on the class, which avoids

    28 #                    needing to override __getattr__().  It will only

    29 #                    work for read-only attributes.

    30 #

    31 #                    For older versions of Python, inheriting from

    32 #                    GetattrMagic will use the traditional

    33 #                    __getattr__() hackery to achieve the same effect,

    34 #                    but less efficiently.

    35 #

    36 #                    defproperty() should be used for each version of

    37 #                    the relevant _get_<property>() function.

    38 

    39 __all__ = ["NodeList", "EmptyNodeList", "StringTypes", "defproperty"]

    40 

    41 import xml.dom

    42 

    43 try:

    44     unicode

    45 except NameError:

    46     StringTypes = type(''),

    47 else:

    48     StringTypes = type(''), type(unicode(''))

    49 

    50 

    51 class NodeList(list):

    52     __slots__ = ()

    53 

    54     def item(self, index):

    55         if 0 <= index < len(self):

    56             return self[index]

    57 

    58     def _get_length(self):

    59         return len(self)

    60 

    61     def _set_length(self, value):

    62         raise xml.dom.NoModificationAllowedErr(

    63             "attempt to modify read-only attribute 'length'")

    64 

    65     length = property(_get_length, _set_length,

    66                       doc="The number of nodes in the NodeList.")

    67 

    68     def __getstate__(self):

    69         return list(self)

    70 

    71     def __setstate__(self, state):

    72         self[:] = state

    73 

    74 

    75 class EmptyNodeList(tuple):

    76     __slots__ = ()

    77 

    78     def __add__(self, other):

    79         NL = NodeList()

    80         NL.extend(other)

    81         return NL

    82 

    83     def __radd__(self, other):

    84         NL = NodeList()

    85         NL.extend(other)

    86         return NL

    87 

    88     def item(self, index):

    89         return None

    90 

    91     def _get_length(self):

    92         return 0

    93 

    94     def _set_length(self, value):

    95         raise xml.dom.NoModificationAllowedErr(

    96             "attempt to modify read-only attribute 'length'")

    97 

    98     length = property(_get_length, _set_length,

    99                       doc="The number of nodes in the NodeList.")

   100 

   101 

   102 def defproperty(klass, name, doc):

   103     get = getattr(klass, ("_get_" + name)).im_func

   104     def set(self, value, name=name):

   105         raise xml.dom.NoModificationAllowedErr(

   106             "attempt to modify read-only attribute " + repr(name))

   107     assert not hasattr(klass, "_set_" + name), \

   108            "expected not to find _set_" + name

   109     prop = property(get, set, doc=doc)

   110     setattr(klass, name, prop)