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bpo-32337: Update documentats about dict order (GH-4973)

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hui shang 2018-04-04 12:55:05 +08:00 • committed by INADA Naoki
parent c869529ea9
commit dfbbbf16f9
4 changed files with 21 additions and 23 deletions
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26
Doc/tutorial/datastructures.rst
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@ -497,7 +497,7 @@ You can't use lists as keys, since lists can be modified in place using index
assignments, slice assignments, or methods like :meth:`append` and
:meth:`extend`.
It is best to think of a dictionary as an unordered set of *key: value* pairs,
It is best to think of a dictionary as a set of *key: value* pairs,
with the requirement that the keys are unique (within one dictionary). A pair of
braces creates an empty dictionary: ``{}``. Placing a comma-separated list of
key:value pairs within the braces adds initial key:value pairs to the
@ -509,9 +509,9 @@ pair with ``del``. If you store using a key that is already in use, the old
value associated with that key is forgotten. It is an error to extract a value
using a non-existent key.
Performing ``list(d.keys())`` on a dictionary returns a list of all the keys
used in the dictionary, in arbitrary order (if you want it sorted, just use
``sorted(d.keys())`` instead). [2]_ To check whether a single key is in the
Performing ``list(d)`` on a dictionary returns a list of all the keys
used in the dictionary, in insertion order (if you want it sorted, just use
``sorted(d)`` instead). To check whether a single key is in the
dictionary, use the :keyword:`in` keyword.
Here is a small example using a dictionary::
@ -519,16 +519,16 @@ Here is a small example using a dictionary::
>>> tel = {'jack': 4098, 'sape': 4139}
>>> tel['guido'] = 4127
>>> tel
{'sape': 4139, 'guido': 4127, 'jack': 4098}
{'jack': 4098, 'sape': 4139, 'guido': 4127}
>>> tel['jack']
4098
>>> del tel['sape']
>>> tel['irv'] = 4127
>>> tel
{'guido': 4127, 'irv': 4127, 'jack': 4098}
>>> list(tel.keys())
['irv', 'guido', 'jack']
>>> sorted(tel.keys())
{'jack': 4098, 'guido': 4127, 'irv': 4127}
>>> list(tel)
['jack', 'guido', 'irv']
>>> sorted(tel)
['guido', 'irv', 'jack']
>>> 'guido' in tel
True
@ -539,7 +539,7 @@ The :func:`dict` constructor builds dictionaries directly from sequences of
key-value pairs::
>>> dict([('sape', 4139), ('guido', 4127), ('jack', 4098)])
{'sape': 4139, 'jack': 4098, 'guido': 4127}
{'sape': 4139, 'guido': 4127, 'jack': 4098}
In addition, dict comprehensions can be used to create dictionaries from
arbitrary key and value expressions::
@ -551,7 +551,7 @@ When the keys are simple strings, it is sometimes easier to specify pairs using
keyword arguments::
>>> dict(sape=4139, guido=4127, jack=4098)
{'sape': 4139, 'jack': 4098, 'guido': 4127}
{'sape': 4139, 'guido': 4127, 'jack': 4098}
.. _tut-loopidioms:
@ -710,7 +710,3 @@ interpreter will raise a :exc:`TypeError` exception.
.. [1] Other languages may return the mutated object, which allows method
chaining, such as ``d->insert("a")->remove("b")->sort();``.
.. [2] Calling ``d.keys()`` will return a :dfn:`dictionary view` object. It
supports operations like membership test and iteration, but its contents
are not independent of the original dictionary -- it is only a *view*.