- Patch 1433928:
- The copy module now "copies" function objects (as atomic objects).
- dict.__getitem__ now looks for a __missing__ hook before raising
KeyError.
- Added a new type, defaultdict, to the collections module.
This uses the new __missing__ hook behavior added to dict (see above).
diff --git a/Doc/lib/libcollections.tex b/Doc/lib/libcollections.tex
index 51603aa..542ef6b 100644
--- a/Doc/lib/libcollections.tex
+++ b/Doc/lib/libcollections.tex
@@ -8,9 +8,10 @@
\versionadded{2.4}
-This module implements high-performance container datatypes. Currently, the
-only datatype is a deque. Future additions may include B-trees
-and Fibonacci heaps.
+This module implements high-performance container datatypes. Currently,
+there are two datatypes, deque and defaultdict.
+Future additions may include B-trees and Fibonacci heaps.
+\versionchanged[Added defaultdict]{2.5}
\begin{funcdesc}{deque}{\optional{iterable}}
Returns a new deque objected initialized left-to-right (using
@@ -211,3 +212,46 @@
[[[['a', 'b'], ['c', 'd']], [['e', 'f'], ['g', 'h']]]]
\end{verbatim}
+
+
+
+\begin{funcdesc}{defaultdict}{\optional{default_factory\optional{, ...}}}
+ Returns a new dictionary-like object. \class{defaultdict} is a subclass
+ of the builtin \class{dict} class. It overrides one method and adds one
+ writable instance variable. The remaining functionality is the same as
+ for the \class{dict} class and is not documented here.
+
+ The first argument provides the initial value for the
+ \member{default_factory} attribute; it defaults to \code{None}.
+ All remaining arguments are treated the same as if they were
+ passed to the \class{dict} constructor, including keyword arguments.
+
+ \versionadded{2.5}
+\end{funcdesc}
+
+\class{defaultdict} objects support the following method in addition to
+the standard \class{dict} operations:
+
+\begin{methoddesc}{__missing__}{key}
+ If the \member{default_factory} attribute is \code{None}, this raises
+ an \exception{KeyError} exception with the \var{key} as argument.
+
+ If \member{default_factory} is not \code{None}, it is called without
+ arguments to provide a default value for the given \var{key}, this
+ value is inserted in the dictionary for the \var{key}, and returned.
+
+ If calling \member{default_factory} raises an exception this exception
+ is propagated unchanged.
+
+ This method is called by the \method{__getitem__} method of the
+ \class{dict} class when the requested key is not found; whatever it
+ returns or raises is then returned or raised by \method{__getitem__}.
+\end{methoddesc}
+
+\class{defaultdict} objects support the following instance variable:
+
+\begin{datadesc}{default_factory}
+ This attribute is used by the \method{__missing__} method; it is initialized
+ from the first argument to the constructor, if present, or to \code{None},
+ if absent.
+\end{datadesc}
diff --git a/Doc/lib/libcopy.tex b/Doc/lib/libcopy.tex
index d73d6fd..5964187 100644
--- a/Doc/lib/libcopy.tex
+++ b/Doc/lib/libcopy.tex
@@ -67,9 +67,12 @@
\end{itemize}
-This version does not copy types like module, class, function, method,
+This module does not copy types like module, method,
stack trace, stack frame, file, socket, window, array, or any similar
-types.
+types. It does ``copy'' functions and classes (shallow and deeply),
+by returning the original object unchanged; this is compatible with
+the way these are treated by the \module{pickle} module.
+\versionchanged[Added copying functions]{2.5}
Classes can use the same interfaces to control copying that they use
to control pickling. See the description of module
diff --git a/Doc/lib/libstdtypes.tex b/Doc/lib/libstdtypes.tex
index 5df39db..5d15375 100644
--- a/Doc/lib/libstdtypes.tex
+++ b/Doc/lib/libstdtypes.tex
@@ -1350,7 +1350,7 @@
\begin{tableiii}{c|l|c}{code}{Operation}{Result}{Notes}
\lineiii{len(\var{a})}{the number of items in \var{a}}{}
- \lineiii{\var{a}[\var{k}]}{the item of \var{a} with key \var{k}}{(1)}
+ \lineiii{\var{a}[\var{k}]}{the item of \var{a} with key \var{k}}{(1), (10)}
\lineiii{\var{a}[\var{k}] = \var{v}}
{set \code{\var{a}[\var{k}]} to \var{v}}
{}
@@ -1454,6 +1454,17 @@
\versionchanged[Allowed the argument to be an iterable of key/value
pairs and allowed keyword arguments]{2.4}
+\item[(10)] If a subclass of dict defines a method \method{__missing__},
+if the key \var{k} is not present, the \var{a}[\var{k}] operation calls
+that method with the key \var{k} as argument. The \var{a}[\var{k}]
+operation then returns or raises whatever is returned or raised by the
+\function{__missing__}(\var{k}) call if the key is not present.
+No other operations or methods invoke \method{__missing__}().
+If \method{__missing__} is not defined, \exception{KeyError} is raised.
+\method{__missing__} must be a method; it cannot be an instance variable.
+For an example, see \module{collections}.\class{defaultdict}.
+\versionadded{2.5}
+
\end{description}
\subsection{File Objects