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| author | Raymond Hettinger <python@rcn.com> | 2008-01-07 09:03:49 (GMT) |
|---|---|---|
| committer | Raymond Hettinger <python@rcn.com> | 2008-01-07 09:03:49 (GMT) |
| commit | dc55f35f387479888019538a429f38104a8bc3b0 (patch) | |
| tree | 5582bf27e456e192338234976edba1a053e0f879 /Doc/library/collections.rst | |
| parent | fd1c24518be99e3e2d0891bf7d2c94fbd4d39367 (diff) | |
| download | cpython-dc55f35f387479888019538a429f38104a8bc3b0.zip cpython-dc55f35f387479888019538a429f38104a8bc3b0.tar.gz cpython-dc55f35f387479888019538a429f38104a8bc3b0.tar.bz2 | |
Add another named tuple subclassing example.
Diffstat (limited to 'Doc/library/collections.rst')
| -rw-r--r-- | Doc/library/collections.rst | 8 |
1 files changed, 8 insertions, 0 deletions
diff --git a/Doc/library/collections.rst b/Doc/library/collections.rst index d7d1083..564c45b 100644 --- a/Doc/library/collections.rst +++ b/Doc/library/collections.rst @@ -527,6 +527,14 @@ a fixed-width print format: 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`: |