jpayne@68: """Python version compatibility support for minidom.
jpayne@68: 
jpayne@68: This module contains internal implementation details and
jpayne@68: should not be imported; use xml.dom.minidom instead.
jpayne@68: """
jpayne@68: 
jpayne@68: # This module should only be imported using "import *".
jpayne@68: #
jpayne@68: # The following names are defined:
jpayne@68: #
jpayne@68: #   NodeList      -- lightest possible NodeList implementation
jpayne@68: #
jpayne@68: #   EmptyNodeList -- lightest possible NodeList that is guaranteed to
jpayne@68: #                    remain empty (immutable)
jpayne@68: #
jpayne@68: #   StringTypes   -- tuple of defined string types
jpayne@68: #
jpayne@68: #   defproperty   -- function used in conjunction with GetattrMagic;
jpayne@68: #                    using these together is needed to make them work
jpayne@68: #                    as efficiently as possible in both Python 2.2+
jpayne@68: #                    and older versions.  For example:
jpayne@68: #
jpayne@68: #                        class MyClass(GetattrMagic):
jpayne@68: #                            def _get_myattr(self):
jpayne@68: #                                return something
jpayne@68: #
jpayne@68: #                        defproperty(MyClass, "myattr",
jpayne@68: #                                    "return some value")
jpayne@68: #
jpayne@68: #                    For Python 2.2 and newer, this will construct a
jpayne@68: #                    property object on the class, which avoids
jpayne@68: #                    needing to override __getattr__().  It will only
jpayne@68: #                    work for read-only attributes.
jpayne@68: #
jpayne@68: #                    For older versions of Python, inheriting from
jpayne@68: #                    GetattrMagic will use the traditional
jpayne@68: #                    __getattr__() hackery to achieve the same effect,
jpayne@68: #                    but less efficiently.
jpayne@68: #
jpayne@68: #                    defproperty() should be used for each version of
jpayne@68: #                    the relevant _get_<property>() function.
jpayne@68: 
jpayne@68: __all__ = ["NodeList", "EmptyNodeList", "StringTypes", "defproperty"]
jpayne@68: 
jpayne@68: import xml.dom
jpayne@68: 
jpayne@68: StringTypes = (str,)
jpayne@68: 
jpayne@68: 
jpayne@68: class NodeList(list):
jpayne@68:     __slots__ = ()
jpayne@68: 
jpayne@68:     def item(self, index):
jpayne@68:         if 0 <= index < len(self):
jpayne@68:             return self[index]
jpayne@68: 
jpayne@68:     def _get_length(self):
jpayne@68:         return len(self)
jpayne@68: 
jpayne@68:     def _set_length(self, value):
jpayne@68:         raise xml.dom.NoModificationAllowedErr(
jpayne@68:             "attempt to modify read-only attribute 'length'")
jpayne@68: 
jpayne@68:     length = property(_get_length, _set_length,
jpayne@68:                       doc="The number of nodes in the NodeList.")
jpayne@68: 
jpayne@68:     # For backward compatibility
jpayne@68:     def __setstate__(self, state):
jpayne@68:         if state is None:
jpayne@68:             state = []
jpayne@68:         self[:] = state
jpayne@68: 
jpayne@68: 
jpayne@68: class EmptyNodeList(tuple):
jpayne@68:     __slots__ = ()
jpayne@68: 
jpayne@68:     def __add__(self, other):
jpayne@68:         NL = NodeList()
jpayne@68:         NL.extend(other)
jpayne@68:         return NL
jpayne@68: 
jpayne@68:     def __radd__(self, other):
jpayne@68:         NL = NodeList()
jpayne@68:         NL.extend(other)
jpayne@68:         return NL
jpayne@68: 
jpayne@68:     def item(self, index):
jpayne@68:         return None
jpayne@68: 
jpayne@68:     def _get_length(self):
jpayne@68:         return 0
jpayne@68: 
jpayne@68:     def _set_length(self, value):
jpayne@68:         raise xml.dom.NoModificationAllowedErr(
jpayne@68:             "attempt to modify read-only attribute 'length'")
jpayne@68: 
jpayne@68:     length = property(_get_length, _set_length,
jpayne@68:                       doc="The number of nodes in the NodeList.")
jpayne@68: 
jpayne@68: 
jpayne@68: def defproperty(klass, name, doc):
jpayne@68:     get = getattr(klass, ("_get_" + name))
jpayne@68:     def set(self, value, name=name):
jpayne@68:         raise xml.dom.NoModificationAllowedErr(
jpayne@68:             "attempt to modify read-only attribute " + repr(name))
jpayne@68:     assert not hasattr(klass, "_set_" + name), \
jpayne@68:            "expected not to find _set_" + name
jpayne@68:     prop = property(get, set, doc=doc)
jpayne@68:     setattr(klass, name, prop)