bpo-29981: Add examples and update index for set, dict, and generator comprehensions'(GH-20272)

Co-authored-by: Rémi Lapeyre <remi.lapeyre@henki.fr>
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Florian Dahlitz 2020-10-20 23:27:07 +02:00 committed by GitHub
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@ -308,6 +308,12 @@ Glossary
keys can be any object with :meth:`__hash__` and :meth:`__eq__` methods.
Called a hash in Perl.
dictionary comprehension
A compact way to process all or part of the elements in an iterable and
return a dictionary with the results. ``results = {n: n ** 2 for n in
range(10)}`` generates a dictionary containing key ``n`` mapped to
value ``n ** 2``. See :ref:`comprehensions`.
dictionary view
The objects returned from :meth:`dict.keys`, :meth:`dict.values`, and
:meth:`dict.items` are called dictionary views. They provide a dynamic
@ -1026,6 +1032,12 @@ Glossary
interface can be registered explicitly using
:func:`~abc.register`.
set comprehension
A compact way to process all or part of the elements in an iterable and
return a set with the results. ``results = {c for c in 'abracadabra' if
c not in 'abc'}`` generates the set of strings ``{'r', 'd'}``. See
:ref:`comprehensions`.
single dispatch
A form of :term:`generic function` dispatch where the implementation is
chosen based on the type of a single argument.

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@ -4140,6 +4140,12 @@ The constructors for both classes work the same:
objects. If *iterable* is not specified, a new empty set is
returned.
Sets can be created by several means:
* Use a comma-separated list of elements within braces: ``{'jack', 'sjoerd'}``
* Use a set comprehension: ``{c for c in 'abracadabra' if c not in 'abc'}``
* Use the type constructor: ``set()``, ``set('foobar')``, ``set(['a', 'b', 'foo'])``
Instances of :class:`set` and :class:`frozenset` provide the following
operations:
@ -4332,6 +4338,14 @@ pairs within braces, for example: ``{'jack': 4098, 'sjoerd': 4127}`` or ``{4098:
Return a new dictionary initialized from an optional positional argument
and a possibly empty set of keyword arguments.
Dictionaries can be created by several means:
* Use a comma-separated list of ``key: value`` pairs within braces:
``{'jack': 4098, 'sjoerd': 4127}`` or ``{4098: 'jack', 4127: 'sjoerd'}``
* Use a dict comprehension: ``{}``, ``{x: x ** 2 for x in range(10)}``
* Use the type constructor: ``dict()``,
``dict([('foo', 100), ('bar', 200)])``, ``dict(foo=100, bar=200)``
If no positional argument is given, an empty dictionary is created.
If a positional argument is given and it is a mapping object, a dictionary
is created with the same key-value pairs as the mapping object. Otherwise,

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@ -162,6 +162,8 @@ ambiguities and allow common typos to pass uncaught.
Displays for lists, sets and dictionaries
-----------------------------------------
.. index:: single: comprehensions
For constructing a list, a set or a dictionary Python provides special syntax
called "displays", each of them in two flavors:
@ -260,6 +262,7 @@ Set displays
.. index::
pair: set; display
pair: set; comprehensions
object: set
single: {} (curly brackets); set expression
single: , (comma); expression list
@ -287,6 +290,7 @@ Dictionary displays
.. index::
pair: dictionary; display
pair: dictionary; comprehensions
key, datum, key/datum pair
object: dictionary
single: {} (curly brackets); dictionary expression

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@ -382,6 +382,7 @@ Brian Curtin
Jason Curtis
Hakan Celik
Paul Dagnelie
Florian Dahlitz
Lisandro Dalcin
Darren Dale
Andrew Dalke