Accept Issac Morland's suggestion for __replace__ to allow multiple replacements

(suprisingly, this simplifies the signature, improves clarity, and is comparably fast).
Update the docs to reflect a previous change to the function name.
Add an example to the docs showing how to override the default __repr__ method.

2 files changed, 9 insertions, 5 deletions

diff --git a/Lib/collections.py b/Lib/collections.py
index 40f5187..6b2e58d 100644
--- a/Lib/collections.py
+++ b/Lib/collections.py
@@ -24,7 +24,7 @@ def namedtuple(typename, field_names, verbose=False):
     11
     >>> Point(**d)                      # convert from a dictionary
     Point(x=11, y=22)
-    >>> p.__replace__('x', 100)         # __replace__() is like str.replace() but targets a named field
+    >>> p.__replace__(x=100)            # __replace__() is like str.replace() but targets named fields
     Point(x=100, y=22)
 
     """
@@ -62,9 +62,9 @@ def namedtuple(typename, field_names, verbose=False):
         def __asdict__(self, dict=dict, zip=zip):
             'Return a new dict mapping field names to their values'
             return dict(zip(%(field_names)r, self))
-        def __replace__(self, field, value, dict=dict, zip=zip):
-            'Return a new %(typename)s object replacing one field with a new value'
-            return %(typename)s(**dict(zip(%(field_names)r, self) + [(field, value)]))  \n''' % locals()
+        def __replace__(self, **kwds):
+            'Return a new %(typename)s object replacing specified fields with new values'
+            return %(typename)s(**dict(self.__asdict__().items() + kwds.items()))  \n''' % locals()
     for i, name in enumerate(field_names):
         template += '        %s = property(itemgetter(%d))\n' % (name, i)
     if verbose:
@@ -98,6 +98,10 @@ if __name__ == '__main__':
     p = Point(x=10, y=20)
     assert p == loads(dumps(p))
 
+    # test and demonstrate ability to override methods
+    Point.__repr__ = lambda self:  'Point(%.3f, %.3f)' % self
+    print p
+
     import doctest
     TestResults = namedtuple('TestResults', 'failed attempted')
     print TestResults(*doctest.testmod())
diff --git a/Lib/test/test_collections.py b/Lib/test/test_collections.py
index 04d4d9d..7c5b2dc 100644
--- a/Lib/test/test_collections.py
+++ b/Lib/test/test_collections.py
@@ -40,7 +40,7 @@ class TestNamedTuple(unittest.TestCase):
         self.assert_('__dict__' not in dir(p))                              # verify instance has no dict
         self.assert_('__weakref__' not in dir(p))
         self.assertEqual(p.__fields__, ('x', 'y'))                          # test __fields__ attribute
-        self.assertEqual(p.__replace__('x', 1), (1, 22))                    # test __replace__ method
+        self.assertEqual(p.__replace__(x=1), (1, 22))                       # test __replace__ method
         self.assertEqual(p.__asdict__(), dict(x=11, y=22))                  # test __dict__ method
 
         # Verify that __fields__ is read-only