[Python-checkins] r54053 - in python/trunk: Doc/lib/libcollections.tex Lib/collections.py Lib/test/test_collections.py Misc/NEWS
raymond.hettinger
python-checkins at python.org
Thu Mar 1 07:16:45 CET 2007
Author: raymond.hettinger
Date: Thu Mar 1 07:16:43 2007
New Revision: 54053
Added:
python/trunk/Lib/test/test_collections.py
Modified:
python/trunk/Doc/lib/libcollections.tex
python/trunk/Lib/collections.py
python/trunk/Misc/NEWS
Log:
Add collections.NamedTuple
Modified: python/trunk/Doc/lib/libcollections.tex
==============================================================================
--- python/trunk/Doc/lib/libcollections.tex (original)
+++ python/trunk/Doc/lib/libcollections.tex Thu Mar 1 07:16:43 2007
@@ -9,14 +9,16 @@
This module implements high-performance container datatypes. Currently,
-there are two datatypes, deque and defaultdict.
+there are two datatypes, deque and defaultdict, and one datatype factory
+function, \function{NamedTuple}.
Future additions may include balanced trees and ordered dictionaries.
\versionchanged[Added defaultdict]{2.5}
+\versionchanged[Added NamedTuple]{2.6}
\subsection{\class{deque} objects \label{deque-objects}}
\begin{funcdesc}{deque}{\optional{iterable}}
- Returns a new deque objected initialized left-to-right (using
+ Returns a new deque object initialized left-to-right (using
\method{append()}) with data from \var{iterable}. If \var{iterable}
is not specified, the new deque is empty.
@@ -339,3 +341,50 @@
>>> d.items()
[('blue', set([2, 4])), ('red', set([1, 3]))]
\end{verbatim}
+
+
+
+\subsection{\function{NamedTuple} datatype factory function \label{named-tuple-factory}}
+
+\begin{funcdesc}{NamedTuple}{typename, fieldnames}
+ Returns a new tuple subclass named \var{typename}. The new subclass is used
+ to create tuple-like objects that have fields accessable by attribute
+ lookup as well as being indexable and iterable. Instances of the subclass
+ also have a helpful docstring (with typename and fieldnames) and a helpful
+ \method{__repr__()} method which lists the tuple contents in a \code{name=value}
+ format.
+ \versionadded{2.6}
+
+ The \var{fieldnames} are specified in a single string and are separated by spaces.
+ Any valid Python identifier may be used for a field name.
+
+ Example:
+ \begin{verbatim}
+ >>> Point = NamedTuple('Point', 'x y')
+ >>> Point.__doc__ # docstring for the new datatype
+ 'Point(x, y)'
+ >>> p = Point(11, y=22) # instantiate with positional or keyword arguments
+ >>> p[0] + p[1] # works just like the tuple (11, 22)
+ 33
+ >>> x, y = p # unpacks just like a tuple
+ >>> x, y
+ (11, 22)
+ >>> p.x + p.y # fields also accessable by name
+ 33
+ >>> p # readable __repr__ with name=value style
+ Point(x=11, y=22)
+ \end{verbatim}
+
+ The use cases are the same as those for tuples. The named factories
+ assign meaning to each tuple position and allow for more readable,
+ self-documenting code. Can also be used to assign field names to tuples
+ returned by the \module{csv} or \module{sqlite3} modules. For example:
+
+ \begin{verbatim}
+ import csv
+ EmployeeRecord = NamedTuple('EmployeeRecord', 'name age title deparment paygrade')
+ for tup in csv.reader(open("employees.csv", "rb")):
+ print EmployeeRecord(*tup)
+ \end{verbatim}
+
+\end{funcdesc}
Modified: python/trunk/Lib/collections.py
==============================================================================
--- python/trunk/Lib/collections.py (original)
+++ python/trunk/Lib/collections.py Thu Mar 1 07:16:43 2007
@@ -1,3 +1,62 @@
-__all__ = ['deque', 'defaultdict']
+__all__ = ['deque', 'defaultdict', 'NamedTuple']
from _collections import deque, defaultdict
+from operator import itemgetter as _itemgetter
+import sys as _sys
+
+def NamedTuple(typename, s):
+ """Returns a new subclass of tuple with named fields.
+
+ >>> Point = NamedTuple('Point', 'x y')
+ >>> Point.__doc__ # docstring for the new class
+ 'Point(x, y)'
+ >>> p = Point(11, y=22) # instantiate with positional args or keywords
+ >>> p[0] + p[1] # works just like the tuple (11, 22)
+ 33
+ >>> x, y = p # unpacks just like a tuple
+ >>> x, y
+ (11, 22)
+ >>> p.x + p.y # fields also accessable by name
+ 33
+ >>> p # readable __repr__ with name=value style
+ Point(x=11, y=22)
+
+ """
+
+ field_names = s.split()
+ nargs = len(field_names)
+
+ def __new__(cls, *args, **kwds):
+ if kwds:
+ try:
+ args += tuple(kwds[name] for name in field_names[len(args):])
+ except KeyError, name:
+ raise TypeError('%s missing required argument: %s' % (typename, name))
+ if len(args) != nargs:
+ raise TypeError('%s takes exactly %d arguments (%d given)' % (typename, nargs, len(args)))
+ return tuple.__new__(cls, args)
+
+ repr_template = '%s(%s)' % (typename, ', '.join('%s=%%r' % name for name in field_names))
+
+ m = dict(vars(tuple)) # pre-lookup superclass methods (for faster lookup)
+ m.update(__doc__= '%s(%s)' % (typename, ', '.join(field_names)),
+ __slots__ = (), # no per-instance dict (so instances are same size as tuples)
+ __new__ = __new__,
+ __repr__ = lambda self, _format=repr_template.__mod__: _format(self),
+ __module__ = _sys._getframe(1).f_globals['__name__'],
+ )
+ m.update((name, property(_itemgetter(index))) for index, name in enumerate(field_names))
+
+ return type(typename, (tuple,), m)
+
+
+if __name__ == '__main__':
+ # verify that instances are pickable
+ from cPickle import loads, dumps
+ Point = NamedTuple('Point', 'x y')
+ p = Point(x=10, y=20)
+ assert p == loads(dumps(p))
+
+ import doctest
+ TestResults = NamedTuple('TestResults', 'failed attempted')
+ print TestResults(*doctest.testmod())
Added: python/trunk/Lib/test/test_collections.py
==============================================================================
--- (empty file)
+++ python/trunk/Lib/test/test_collections.py Thu Mar 1 07:16:43 2007
@@ -0,0 +1,57 @@
+import unittest
+from test import test_support
+from collections import NamedTuple
+
+class TestNamedTuple(unittest.TestCase):
+
+ def test_factory(self):
+ Point = NamedTuple('Point', 'x y')
+ self.assertEqual(Point.__name__, 'Point')
+ self.assertEqual(Point.__doc__, 'Point(x, y)')
+ self.assertEqual(Point.__slots__, ())
+ self.assertEqual(Point.__module__, __name__)
+ self.assertEqual(Point.__getitem__, tuple.__getitem__)
+ self.assert_('__getitem__' in Point.__dict__) # superclass methods localized
+
+ def test_instance(self):
+ Point = NamedTuple('Point', 'x y')
+ p = Point(11, 22)
+ self.assertEqual(p, Point(x=11, y=22))
+ self.assertEqual(p, Point(11, y=22))
+ self.assertEqual(p, Point(y=22, x=11))
+ self.assertEqual(p, Point(*(11, 22)))
+ self.assertEqual(p, Point(**dict(x=11, y=22)))
+ self.assertRaises(TypeError, Point, 1) # too few args
+ self.assertRaises(TypeError, Point, 1, 2, 3) # too many args
+ self.assertRaises(TypeError, eval, 'Point(XXX=1, y=2)', locals()) # wrong keyword argument
+ self.assertRaises(TypeError, eval, 'Point(x=1)', locals()) # missing keyword argument
+ 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))
+
+ def test_tupleness(self):
+ Point = NamedTuple('Point', 'x y')
+ p = Point(11, 22)
+
+ self.assert_(isinstance(p, tuple))
+ self.assertEqual(p, (11, 22)) # matches a real tuple
+ self.assertEqual(tuple(p), (11, 22)) # coercable to a real tuple
+ self.assertEqual(list(p), [11, 22]) # coercable to a list
+ self.assertEqual(max(p), 22) # iterable
+ self.assertEqual(max(*p), 22) # star-able
+ x, y = p
+ self.assertEqual(p, (x, y)) # unpacks like a tuple
+ self.assertEqual((p[0], p[1]), (11, 22)) # indexable like a tuple
+ self.assertRaises(IndexError, p.__getitem__, 3)
+
+ self.assertEqual(p.x, x)
+ self.assertEqual(p.y, y)
+ self.assertRaises(AttributeError, eval, 'p.z', locals())
+
+
+def test_main(verbose=None):
+ test_classes = [TestNamedTuple]
+ test_support.run_unittest(*test_classes)
+
+if __name__ == "__main__":
+ test_main(verbose=True)
Modified: python/trunk/Misc/NEWS
==============================================================================
--- python/trunk/Misc/NEWS (original)
+++ python/trunk/Misc/NEWS Thu Mar 1 07:16:43 2007
@@ -138,6 +138,8 @@
- Added heapq.merge() for merging sorted input streams.
+- Added collections.NamedTuple() for assigning field names to tuples.
+
- Added itertools.izip_longest().
- Have the encoding package's search function dynamically import using absolute
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