Copied doc for reload() from trunk's function.rst to imp.rst
diff --git a/Doc/library/collections.rst b/Doc/library/collections.rst
index 5b625ee..cb3a029 100644
--- a/Doc/library/collections.rst
+++ b/Doc/library/collections.rst
@@ -489,7 +489,7 @@
>>> Point._make(t)
Point(x=11, y=22)
-.. method:: somenamedtuple._asdict()
+.. method:: namedtuple._asdict()
Return a new dict which maps field names to their corresponding values:
@@ -498,7 +498,7 @@
>>> p._asdict()
{'x': 11, 'y': 22}
-.. method:: somenamedtuple._replace(kwargs)
+.. method:: namedtuple._replace(kwargs)
Return a new instance of the named tuple replacing specified fields with new values:
@@ -511,7 +511,7 @@
>>> for partnum, record in inventory.items():
... inventory[partnum] = record._replace(price=newprices[partnum], updated=time.now())
-.. attribute:: somenamedtuple._fields
+.. attribute:: namedtuple._fields
Tuple of strings listing the field names. This is useful for introspection
and for creating new named tuple types from existing named tuples.
@@ -541,15 +541,28 @@
Point(x=11, y=22)
Since a named tuple is a regular Python class, it is easy to add or change
-functionality. For example, the display format can be changed by overriding
-the :meth:`__repr__` method:
+functionality with a subclass. Here is how to add a calculated field and
+a fixed-width print format::
-::
+ >>> class Point(namedtuple('Point', 'x y')):
+ @property
+ def hypot(self):
+ return (self.x ** 2 + self.y ** 2) ** 0.5
+ def __repr__(self):
+ return 'Point(x=%.3f, y=%.3f, hypot=%.3f)' % (self.x, self.y, self.hypot)
- >>> Point = namedtuple('Point', 'x y')
- >>> Point.__repr__ = lambda self: 'Point(%.3f, %.3f)' % self
- >>> Point(x=11, y=22)
- Point(11.000, 22.000)
+ >>> print Point(3, 4),'\n', Point(2, 5), '\n', Point(9./7, 6)
+ Point(x=3.000, y=4.000, hypot=5.000)
+ Point(x=2.000, y=5.000, hypot=5.385)
+ Point(x=1.286, y=6.000, hypot=6.136)
+
+Another use for subclassing is to replace performance critcal methods with
+faster versions that bypass error-checking and localize variable access::
+
+ >>> class Point(namedtuple('Point', 'x y')):
+ _make = classmethod(tuple.__new__)
+ def _replace(self, _map=map, **kwds):
+ return self._make(_map(kwds.pop, ('x', 'y'), self))
Default values can be implemented by starting with a prototype instance
and customizing it with :meth:`_replace`: