stub for special-method-names chapter

examples/ordereddict.py

@@ -0,0 +1,83 @@
+#
+# OrderedDict will be part of the collections module in Python 3.1.
+# This is a standalone version for demonstration purposes only.
+# If you're using Python 3.0, you should upgrade to Python 3.1, then
+# >>> from collections import OrderedDict
+# instead of using this version.
+#
+# Provenance:
+# - PEP 372: OrderedDict http://www.python.org/dev/peps/pep-0372/
+# - Python bug 5397: implement PEP 372 http://bugs.python.org/issue5397
+# - Bug 5397 attachment: http://bugs.python.org/file13231/od7.diff
+#
+
+from collections import MutableMapping
+from itertools import zip_longest as _zip_longest
+ 
+class OrderedDict(dict, MutableMapping):
+
+    def __init__(self, *args, **kwds):
+        if len(args) > 1:
+            raise TypeError('expected at most 1 arguments')
+        if not hasattr(self, '_keys'):
+            self._keys = []
+        self.update(*args, **kwds)
+
+    def clear(self):
+        del self._keys[:]
+        dict.clear(self)
+
+    def __setitem__(self, key, value):
+        if key not in self:
+            self._keys.append(key)
+        dict.__setitem__(self, key, value)
+
+    def __delitem__(self, key):
+        dict.__delitem__(self, key)
+        self._keys.remove(key)
+
+    def __iter__(self):
+        return iter(self._keys)
+
+    def __reversed__(self):
+        return reversed(self._keys)
+
+    def popitem(self):
+        if not self:
+            raise KeyError('dictionary is empty')
+        key = self._keys.pop()
+        value = dict.pop(self, key)
+        return key, value
+
+    def __reduce__(self):
+        items = [[k, self[k]] for k in self]
+        inst_dict = vars(self).copy()
+        inst_dict.pop('_keys', None)
+        return (self.__class__, (items,), inst_dict)
+
+    setdefault = MutableMapping.setdefault
+    update = MutableMapping.update
+    pop = MutableMapping.pop
+    keys = MutableMapping.keys
+    values = MutableMapping.values
+    items = MutableMapping.items
+
+    def __repr__(self):
+        if not self:
+            return '%s()' % (self.__class__.__name__,)
+        return '%s(%r)' % (self.__class__.__name__, list(self.items()))
+
+    def copy(self):
+        return self.__class__(self)
+
+    @classmethod
+    def fromkeys(cls, iterable, value=None):
+        d = cls()
+        for key in iterable:
+            d[key] = value
+        return d
+
+    def __eq__(self, other):
+        if isinstance(other, OrderedDict):
+            return all(p==q for p, q in  _zip_longest(self.items(), other.items()))
+        return dict.__eq__(self, other)