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author | Raymond Hettinger <python@rcn.com> | 2005-07-01 23:00:13 (GMT) |
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committer | Raymond Hettinger <python@rcn.com> | 2005-07-01 23:00:13 (GMT) |
commit | 16ffbc3d104fff10bf351fbf71b6342694b86dbc (patch) | |
tree | bf4fd7dcf4910ec38bbc290e83455ebd73a27ddb /Doc/lib/libsets.tex | |
parent | c418cc81ae593743cd8c5bf5491c0af72b21749f (diff) | |
download | cpython-16ffbc3d104fff10bf351fbf71b6342694b86dbc.zip cpython-16ffbc3d104fff10bf351fbf71b6342694b86dbc.tar.gz cpython-16ffbc3d104fff10bf351fbf71b6342694b86dbc.tar.bz2 |
Provide a comparison to the builtin set types.
Diffstat (limited to 'Doc/lib/libsets.tex')
-rw-r--r-- | Doc/lib/libsets.tex | 34 |
1 files changed, 32 insertions, 2 deletions
diff --git a/Doc/lib/libsets.tex b/Doc/lib/libsets.tex index 0cd5e2e..e90e527 100644 --- a/Doc/lib/libsets.tex +++ b/Doc/lib/libsets.tex @@ -133,7 +133,7 @@ The following table lists operations available in \class{Set} but not found in \class{ImmutableSet}: \begin{tableiii}{c|c|l}{code}{Operation}{Equivalent}{Result} - \lineiii{\var{s}.union_update(\var{t})} + \lineiii{\var{s}.update(\var{t})} {\var{s} \textbar= \var{t}} {return set \var{s} with elements added from \var{t}} \lineiii{\var{s}.intersection_update(\var{t})} @@ -161,12 +161,17 @@ but not found in \class{ImmutableSet}: {remove all elements from set \var{s}} \end{tableiii} -Note, the non-operator versions of \method{union_update()}, +Note, the non-operator versions of \method{update()}, \method{intersection_update()}, \method{difference_update()}, and \method{symmetric_difference_update()} will accept any iterable as an argument. \versionchanged[Formerly all arguments were required to be sets]{2.3.1} +Also note, the module also includes a \method{union_update()} method +which is an alias for \method{update()}. The method is included for +backwards compatability. Programmers should prefer the +\method{update()} method because it the one supported by the builtin +\class{set()} and \class{frozenset()} types. \subsection{Example \label{set-example}} @@ -231,3 +236,28 @@ user; however, a conflict can arise in a multi-threaded environment where one thread is updating a set while another has temporarily wrapped it in \class{_TemporarilyImmutableSet}. In other words, sets of mutable sets are not thread-safe. + + +\subsection{Comparison to the built-in \class{set} types + \label{comparison-to-builtin-set}} + +The built-in \class{set} and \class{frozenset} types were designed based +on lessons learned from the \module{sets} module. The key differences are: + +\begin{itemize} +\item \class{Set} and \class{ImmutableSet} were renamed to \class{set} and + \class{frozenset}. +\item There is no equivalent to \class{BaseSet}. Instead, use + \code{isinstance(x, (set, frozenset))}. +\item The hash algorithm for the built-ins performs significantly better + (fewer collisions) for most datasets. +\item The built-in versions have more space efficient pickles. +\item The built-in versions do not have a \method{union_update()} method. + Instead, use the \method{update()} method which is equivalent. +\item The built-in versions do not have a \method{_repr(sort=True)} method. + Instead, use the built-in \function{repr()} and \function{sorted()} + functions: \code{repr(sorted(s))}. +\item The built-in version does not have a protocol for automatic conversion + to immutable. Many found this feature to be confusing and no one + in the community reported having found real uses for it. +\end{itemize} |