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Extend some comments on the order of values in the returns from 

dict.items/keys/values/iteritems/iterkeys/itervalues().
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Fred Drake 2002-08-19 21:58:58 +00:00
parent 45ec02aed1
commit 017778332f
1 changed files with 14 additions and 8 deletions
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22
Doc/lib/libstdtypes.tex
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@ -1049,13 +1049,13 @@ arbitrary objects):
{(6)}
\lineiii{\var{a}.iteritems()}
{return an iterator over (\var{key}, \var{value}) pairs}
{(2)}
{(2), (3)}
\lineiii{\var{a}.iterkeys()}
{return an iterator over the mapping's keys}
{(2)}
{(2), (3)}
\lineiii{\var{a}.itervalues()}
{return an iterator over the mapping's values}
{(2)}
{(2), (3)}
\end{tableiii}
\noindent
@ -1067,11 +1067,17 @@ in the map.
\item[(2)] \versionadded{2.2}
\item[(3)] Keys and values are listed in random order. If
\method{keys()} and \method{values()} are called with no intervening
modifications to the dictionary, the two lists will directly
correspond. This allows the creation of \code{(\var{value},
\var{key})} pairs using \function{zip()}: \samp{pairs =
zip(\var{a}.values(), \var{a}.keys())}.
\method{items()}, \method{keys()}, \method{values()},
\method{iteritems()}, \method{iterkeys()}, and \method{itervalues()}
are called with no intervening modifications to the dictionary, the
lists will directly correspond. This allows the creation of
\code{(\var{value}, \var{key})} pairs using \function{zip()}:
\samp{pairs = zip(\var{a}.values(), \var{a}.keys())}. The same
relationship holds for the \method{iterkeys()} and
\method{itervalues()} methods: \samp{pairs = zip(\var{a}.itervalues(),
\var{a}.iterkeys())} provides the same value for \code{pairs}.
Another way to create the same list is \samp{pairs = [(v, k) for (k,
v) in \var{a}.iteritems()]}.
\item[(4)] Never raises an exception if \var{k} is not in the map,
instead it returns \var{x}. \var{x} is optional; when \var{x} is not