Cleaner method naming convention

Doc/library/collections.rst

@@ -368,8 +368,8 @@ they add the ability to access fields by name instead of position index.
    can be specified as a list of strings (such as ['x', 'y']).
 
    Any valid Python identifier may be used for a fieldname except for names
-   starting and ending with double underscores.  Valid identifiers consist of
-   letters, digits, and underscores but do not start with a digit and cannot be
+   starting with an underscore.  Valid identifiers consist of letters, digits,
+   and underscores but do not start with a digit or underscore and cannot be
    a :mod:`keyword` such as *class*, *for*, *return*, *global*, *pass*, *print*,
    or *raise*.
 
@@ -386,15 +386,15 @@ Example::
    class Point(tuple):
            'Point(x, y)'
            __slots__ = ()
-           __fields__ = ('x', 'y')
+           _fields = ('x', 'y')
            def __new__(cls, x, y):
                return tuple.__new__(cls, (x, y))
            def __repr__(self):
                return 'Point(x=%r, y=%r)' % self
-           def __asdict__(self):
+           def _asdict(self):
                'Return a new dict mapping field names to their values'
                return dict(zip(('x', 'y'), self))
-           def __replace__(self, **kwds):
+           def _replace(self, **kwds):
                'Return a new Point object replacing specified fields with new values'
                return Point(**dict(zip(('x', 'y'), self), **kwds))
            x = property(itemgetter(0))
@@ -444,40 +444,40 @@ When casting a dictionary to a named tuple, use the double-star-operator::
 In addition to the methods inherited from tuples, named tuples support
 two additonal methods and a read-only attribute.
 
-.. method:: somenamedtuple.__asdict__()
+.. method:: somenamedtuple._asdict()
 
    Return a new dict which maps field names to their corresponding values:
 
 ::
 
-      >>> p.__asdict__()
+      >>> p._asdict()
       {'x': 11, 'y': 22}
       
-.. method:: somenamedtuple.__replace__(kwargs)
+.. method:: somenamedtuple._replace(kwargs)
 
    Return a new instance of the named tuple replacing specified fields with new values:
 
 ::
 
       >>> p = Point(x=11, y=22)
-      >>> p.__replace__(x=33)
+      >>> p._replace(x=33)
       Point(x=33, y=22)
 
       >>> for partnum, record in inventory.items():
-      ...     inventory[partnum] = record.__replace__(price=newprices[partnum], updated=time.now())
+      ...     inventory[partnum] = record._replace(price=newprices[partnum], updated=time.now())
 
-.. attribute:: somenamedtuple.__fields__
+.. attribute:: somenamedtuple._fields
 
    Return a tuple of strings listing the field names.  This is useful for introspection
    and for creating new named tuple types from existing named tuples.
 
 ::
 
-      >>> p.__fields__                                  # view the field names
+      >>> p._fields            # view the field names
       ('x', 'y')
 
       >>> Color = namedtuple('Color', 'red green blue')
-      >>> Pixel = namedtuple('Pixel', Point.__fields__ + Color.__fields__)
+      >>> Pixel = namedtuple('Pixel', Point._fields + Color._fields)
       >>> Pixel(11, 22, 128, 255, 0)
       Pixel(x=11, y=22, red=128, green=255, blue=0)'
 
@@ -493,13 +493,13 @@ the :meth:`__repr__` method:
     Point(10.000, 20.000)
 
 Default values can be implemented by starting with a prototype instance
-and customizing it with :meth:`__replace__`:
+and customizing it with :meth:`_replace`:
 
 ::
 
     >>> Account = namedtuple('Account', 'owner balance transaction_count')
     >>> model_account = Account('<owner name>', 0.0, 0)
-    >>> johns_account = model_account.__replace__(owner='John')
+    >>> johns_account = model_account._replace(owner='John')
 
 .. rubric:: Footnotes
 

Lib/collections.py

@@ -26,12 +26,12 @@ def namedtuple(typename, field_names, verbose=False):
     (11, 22)
     >>> p.x + p.y                       # fields also accessable by name
     33
-    >>> d = p.__asdict__()              # convert to a dictionary
+    >>> d = p._asdict()                 # convert to a dictionary
     >>> d['x']
     11
     >>> Point(**d)                      # convert from a dictionary
     Point(x=11, y=22)
-    >>> p.__replace__(x=100)            # __replace__() is like str.replace() but targets named fields
+    >>> p._replace(x=100)               # _replace() is like str.replace() but targets named fields
     Point(x=100, y=22)
 
     """
@@ -49,8 +49,8 @@ def namedtuple(typename, field_names, verbose=False):
             raise ValueError('Type names and field names cannot start with a number: %r' % name)
     seen_names = set()
     for name in field_names:
-        if name.startswith('__') and name.endswith('__') and len(name) > 3:
-            raise ValueError('Field names cannot start and end with double underscores: %r' % name)
+        if name.startswith('_'):
+            raise ValueError('Field names cannot start with an underscore: %r' % name)
         if name in seen_names:
             raise ValueError('Encountered duplicate field name: %r' % name)
         seen_names.add(name)
@@ -61,15 +61,15 @@ def namedtuple(typename, field_names, verbose=False):
     template = '''class %(typename)s(tuple):
         '%(typename)s(%(argtxt)s)'
         __slots__ = ()
-        __fields__ = property(lambda self: %(field_names)r)
+        _fields = property(lambda self: %(field_names)r)
         def __new__(cls, %(argtxt)s):
             return tuple.__new__(cls, (%(argtxt)s))
         def __repr__(self):
             return '%(typename)s(%(reprtxt)s)' %% self
-        def __asdict__(self, dict=dict, zip=zip):
+        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, **kwds):
+        def _replace(self, **kwds):
             'Return a new %(typename)s object replacing specified fields with new values'
             return %(typename)s(**dict(zip(%(field_names)r, self), **kwds))  \n''' % locals()
     for i, name in enumerate(field_names):

Lib/test/test_collections.py

@@ -25,11 +25,11 @@ class TestNamedTuple(unittest.TestCase):
         self.assertRaises(ValueError, namedtuple, 'abc', 'efg g%hi')       # field with non-alpha char
         self.assertRaises(ValueError, namedtuple, 'abc', 'abc class')      # field has keyword
         self.assertRaises(ValueError, namedtuple, 'abc', '8efg 9ghi')      # field starts with digit
-        self.assertRaises(ValueError, namedtuple, 'abc', '__efg__ ghi')    # field with double underscores
+        self.assertRaises(ValueError, namedtuple, 'abc', '_efg ghi')       # field with leading underscore
         self.assertRaises(ValueError, namedtuple, 'abc', 'efg efg ghi')    # duplicate field
 
         namedtuple('Point0', 'x1 y2')   # Verify that numbers are allowed in names
-        namedtuple('_', '_ __ ___')     # Verify that underscores are allowed
+        namedtuple('_', 'a b c')        # Test leading underscores in a typename
 
     def test_instance(self):
         Point = namedtuple('Point', 'x y')
@@ -46,17 +46,17 @@ class TestNamedTuple(unittest.TestCase):
         self.assertEqual(repr(p), 'Point(x=11, y=22)')
         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.__asdict__(), dict(x=11, y=22))                  # test __dict__ method
+        self.assertEqual(p._fields, ('x', 'y'))                             # test _fields attribute
+        self.assertEqual(p._replace(x=1), (1, 22))                          # test _replace method
+        self.assertEqual(p._asdict(), dict(x=11, y=22))                     # test _asdict method
 
-        # Verify that __fields__ is read-only
+        # Verify that _fields is read-only
         try:
-            p.__fields__ = ('F1' ,'F2')
+            p._fields = ('F1' ,'F2')
         except AttributeError:
             pass
         else:
-            self.fail('The __fields__ attribute needs to be read-only')
+            self.fail('The _fields attribute needs to be read-only')
 
         # verify that field string can have commas
         Point = namedtuple('Point', 'x, y')