1 files changed, 46 insertions, 12 deletions
diff --git a/Lib/UserString.py b/Lib/UserString.py
index 60dc34bc4b..726b3f7d3c 100755
--- a/Lib/UserString.py
+++ b/Lib/UserString.py
@@ -6,10 +6,11 @@ Note: string objects have grown methods in Python 1.6
 This module requires Python 1.6 or later.
 """
 import sys
+import collections
 
 __all__ = ["UserString","MutableString"]
 
-class UserString:
+class UserString(collections.Sequence):
     def __init__(self, seq):
         if isinstance(seq, basestring):
             self.data = seq
@@ -129,7 +130,7 @@ class UserString:
     def upper(self): return self.__class__(self.data.upper())
     def zfill(self, width): return self.__class__(self.data.zfill(width))
 
-class MutableString(UserString):
+class MutableString(UserString, collections.MutableSequence):
     """mutable string objects
 
     Python strings are immutable objects.  This has the advantage, that
@@ -145,19 +146,50 @@ class MutableString(UserString):
 
     A faster and better solution is to rewrite your program using lists."""
     def __init__(self, string=""):
+        from warnings import warnpy3k
+        warnpy3k('the class UserString.MutableString has been removed in '
+                    'Python 3.0', stacklevel=2)
         self.data = string
-    def __hash__(self):
-        raise TypeError, "unhashable type (it is mutable)"
+
+    # We inherit object.__hash__, so we must deny this explicitly
+    __hash__ = None
+
     def __setitem__(self, index, sub):
-        if index < 0:
-            index += len(self.data)
-        if index < 0 or index >= len(self.data): raise IndexError
-        self.data = self.data[:index] + sub + self.data[index+1:]
+        if isinstance(index, slice):
+            if isinstance(sub, UserString):
+                sub = sub.data
+            elif not isinstance(sub, basestring):
+                sub = str(sub)
+            start, stop, step = index.indices(len(self.data))
+            if step == -1:
+                start, stop = stop+1, start+1
+                sub = sub[::-1]
+            elif step != 1:
+                # XXX(twouters): I guess we should be reimplementing
+                # the extended slice assignment/deletion algorithm here...
+                raise TypeError, "invalid step in slicing assignment"
+            start = min(start, stop)
+            self.data = self.data[:start] + sub + self.data[stop:]
+        else:
+            if index < 0:
+                index += len(self.data)
+            if index < 0 or index >= len(self.data): raise IndexError
+            self.data = self.data[:index] + sub + self.data[index+1:]
     def __delitem__(self, index):
-        if index < 0:
-            index += len(self.data)
-        if index < 0 or index >= len(self.data): raise IndexError
-        self.data = self.data[:index] + self.data[index+1:]
+        if isinstance(index, slice):
+            start, stop, step = index.indices(len(self.data))
+            if step == -1:
+                start, stop = stop+1, start+1
+            elif step != 1:
+                # XXX(twouters): see same block in __setitem__
+                raise TypeError, "invalid step in slicing deletion"
+            start = min(start, stop)
+            self.data = self.data[:start] + self.data[stop:]
+        else:
+            if index < 0:
+                index += len(self.data)
+            if index < 0 or index >= len(self.data): raise IndexError
+            self.data = self.data[:index] + self.data[index+1:]
     def __setslice__(self, start, end, sub):
         start = max(start, 0); end = max(end, 0)
         if isinstance(sub, UserString):
@@ -182,6 +214,8 @@ class MutableString(UserString):
     def __imul__(self, n):
         self.data *= n
         return self
+    def insert(self, index, value):
+        self[index:index] = value
 
 if __name__ == "__main__":
     # execute the regression test to stdout, if called as a script: