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Document __copy__() and __deepcopy__() methods.

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Guido van Rossum 1998-06-30 16:54:33 +00:00
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Doc/lib/libcopy.tex
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@ -57,7 +57,7 @@ Python's \code{deepcopy()} operation avoids these problems by:
\begin{itemize} \begin{itemize}
\item \item
keeping a table of objects already copied during the current keeping a ``memo'' dictionary of objects already copied during the current
copying pass; and copying pass; and
\item \item
@ -75,8 +75,21 @@ to control pickling: they can define methods called
\code{__getinitargs__()}, \code{__getstate__()} and \code{__getinitargs__()}, \code{__getstate__()} and
\code{__setstate__()}. See the description of module \code{pickle} \code{__setstate__()}. See the description of module \code{pickle}
for information on these methods. for information on these methods.
The copy module does not use the \module{copy_reg} registration
module.
\refstmodindex{pickle} \refstmodindex{pickle}
\setindexsubitem{(copy protocol)} \setindexsubitem{(copy protocol)}
\ttindex{__getinitargs__} \ttindex{__getinitargs__}
\ttindex{__getstate__} \ttindex{__getstate__}
\ttindex{__setstate__} \ttindex{__setstate__}
In order for a class to define its own copy implementation, it can
define special methods \method{__copy__()}\ttindex{__copy__} and
\method{__deepcopy__()}\ttindex{__deepcopy__}. The former is called to
implement the shallow copy operation; no additional arguments are
passed. The latter is called to implement the deep copy operation; it
is passed one argument, the memo dictionary. If the
\method{__deepcopy__()} implementation needs to make a deep copy of a
component, it should call the \function{deepcopy()} function with the
component as first argument and the memo dictionary as second
argument.