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author | Christian Heimes <christian@cheimes.de> | 2007-12-15 01:27:15 (GMT) |
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committer | Christian Heimes <christian@cheimes.de> | 2007-12-15 01:27:15 (GMT) |
commit | 0449f63f53fa0c2fcf779703d2db77d8a658cf7d (patch) | |
tree | f7e541fe54279a4b5954b79f529d652e659e6bd9 /Doc/library | |
parent | 54cc54c1fe26328d62c70fa55350ad89868c1d61 (diff) | |
download | cpython-0449f63f53fa0c2fcf779703d2db77d8a658cf7d.zip cpython-0449f63f53fa0c2fcf779703d2db77d8a658cf7d.tar.gz cpython-0449f63f53fa0c2fcf779703d2db77d8a658cf7d.tar.bz2 |
Merged revisions 59488-59511 via svnmerge from
svn+ssh://pythondev@svn.python.org/python/trunk
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r59489 | christian.heimes | 2007-12-14 03:33:57 +0100 (Fri, 14 Dec 2007) | 1 line
Silence a warning about an unsed variable in debug builds
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r59490 | christian.heimes | 2007-12-14 03:35:23 +0100 (Fri, 14 Dec 2007) | 2 lines
Fixed bug #1620: New @spam.getter property syntax modifies the property in place.
I added also the feature that a @prop.getter decorator does not overwrite the doc string of the property if it was given as an argument to property().
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r59491 | raymond.hettinger | 2007-12-14 03:49:47 +0100 (Fri, 14 Dec 2007) | 1 line
Cleaner method naming convention
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r59492 | christian.heimes | 2007-12-14 04:02:34 +0100 (Fri, 14 Dec 2007) | 1 line
Fixed a warning in _codecs_iso2022.c and some non C89 conform // comments.
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r59493 | christian.heimes | 2007-12-14 05:38:13 +0100 (Fri, 14 Dec 2007) | 1 line
Fixed warning in ssl module
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r59500 | raymond.hettinger | 2007-12-14 19:08:20 +0100 (Fri, 14 Dec 2007) | 1 line
Add line spacing for readability
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r59501 | raymond.hettinger | 2007-12-14 19:12:21 +0100 (Fri, 14 Dec 2007) | 3 lines
Update method names for named tuples.
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r59503 | georg.brandl | 2007-12-14 20:03:36 +0100 (Fri, 14 Dec 2007) | 3 lines
Add a section about nested listcomps to the tutorial.
Thanks to Ian Bruntlett and Robert Lehmann.
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r59504 | raymond.hettinger | 2007-12-14 20:19:59 +0100 (Fri, 14 Dec 2007) | 1 line
Faster and simpler _replace() method
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r59505 | raymond.hettinger | 2007-12-14 22:51:50 +0100 (Fri, 14 Dec 2007) | 1 line
Add usage note
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r59507 | andrew.kuchling | 2007-12-14 23:41:18 +0100 (Fri, 14 Dec 2007) | 1 line
Remove warning about URL
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r59510 | andrew.kuchling | 2007-12-14 23:52:36 +0100 (Fri, 14 Dec 2007) | 1 line
Bump the version number, and make a few small edits
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r59511 | christian.heimes | 2007-12-15 00:42:36 +0100 (Sat, 15 Dec 2007) | 2 lines
Fixed bug #1628
The detection now works on Unix with Makefile, Makefile with VPATH and on Windows.
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Diffstat (limited to 'Doc/library')
-rw-r--r-- | Doc/library/collections.rst | 53 |
1 files changed, 34 insertions, 19 deletions
diff --git a/Doc/library/collections.rst b/Doc/library/collections.rst index 3ac95b1..1982187 100644 --- a/Doc/library/collections.rst +++ b/Doc/library/collections.rst @@ -403,8 +403,8 @@ 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*. @@ -418,18 +418,25 @@ Example:: >>> Point = namedtuple('Point', 'x y', verbose=True) 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): - 'Return a new dict mapping field names to their values' + + def _asdict(self): + 'Return a new dict which maps 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)) + return Point(*map(kwds.get, ('x', 'y'), self)) + x = property(itemgetter(0)) y = property(itemgetter(1)) @@ -477,43 +484,51 @@ 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)' +To retrieve a field whose name is stored in a string, use the :func:`getattr` +function: + +:: + + >>> getattr(p, 'x') + 11 + 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: @@ -522,17 +537,17 @@ the :meth:`__repr__` method: >>> Point = namedtuple('Point', 'x y') >>> Point.__repr__ = lambda self: 'Point(%.3f, %.3f)' % self - >>> Point(x=10, y=20) - Point(10.000, 20.000) + >>> Point(x=11, y=22) + Point(11.000, 22.000) 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 |