Kaydet (Commit) 8984370c authored tarafından Georg Brandl's avatar Georg Brandl

Bug #1565919: document set types in the Language Reference.

 (backport from rev. 52297)
üst f0db92a6
...@@ -379,6 +379,41 @@ additional example of a mutable sequence type. ...@@ -379,6 +379,41 @@ additional example of a mutable sequence type.
\end{description} % Sequences \end{description} % Sequences
\item[Set types]
These represent unordered, finite sets of unique, immutable objects.
As such, they cannot be indexed by any subscript. However, they can be
iterated over, and the built-in function \function{len()} returns the
number of items in a set. Common uses for sets are
fast membership testing, removing duplicates from a sequence, and
computing mathematical operations such as intersection, union, difference,
and symmetric difference.
\bifuncindex{len}
\obindex{set type}
For set elements, the same immutability rules apply as for dictionary
keys. Note that numeric types obey the normal rules for numeric
comparison: if two numbers compare equal (e.g., \code{1} and
\code{1.0}), only one of them can be contained in a set.
There are currently two intrinsic set types:
\begin{description}
\item[Sets]
These\obindex{set} represent a mutable set. They are created by the
built-in \function{set()} constructor and can be modified afterwards
by several methods, such as \method{add()}.
\item[Frozen sets]
These\obindex{frozenset} represent an immutable set. They are created by
the built-in \function{frozenset()} constructor. As a frozenset is
immutable and hashable, it can be used again as an element of another set,
or as a dictionary key.
\end{description} % Set types
\item[Mappings] \item[Mappings]
These represent finite sets of objects indexed by arbitrary index sets. These represent finite sets of objects indexed by arbitrary index sets.
The subscript notation \code{a[k]} selects the item indexed The subscript notation \code{a[k]} selects the item indexed
......
...@@ -191,6 +191,8 @@ Tests ...@@ -191,6 +191,8 @@ Tests
Documentation Documentation
------------- -------------
- Bug #1565919: document set types in the Language Reference.
- Bug #1546052: clarify that PyString_FromString(AndSize) copies the - Bug #1546052: clarify that PyString_FromString(AndSize) copies the
string pointed to by its parameter. string pointed to by its parameter.
......
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