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Improve the descriptions of expected exceptions for __getitem__(),

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__setitem__(), and __delitem__().  Based on related comments from
Barry Warsaw.
This commit is contained in:
Fred Drake 2000-07-13 04:57:58 +00:00
parent 8d2f2b2db2
commit 91826ed2a9
1 changed files with 14 additions and 4 deletions
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18
Doc/ref/ref3.tex
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@ -1091,9 +1091,16 @@ returns zero is considered to be false in a Boolean context.
\begin{methoddesc}[mapping object]{__getitem__}{self, key}
Called to implement evaluation of \code{\var{self}[\var{key}]}.
For a sequence types, the accepted keys should be integers. Note that the
special interpretation of negative indices (if the class wishes to
For a sequence types, the accepted keys should be integers. Note that
the special interpretation of negative indices (if the class wishes to
emulate a sequence type) is up to the \method{__getitem__()} method.
If \var{key} is of an inappropriate type, \exception{TypeError} may be
raised; if of a value outside the set of indexes for the sequence
(after any special interpretation of negative values),
\exception{IndexError} should be raised.
\strong{Note:} \keyword{for} loops expect that an
\exception{IndexError} will be raised for illegal indexes to allow
proper detection of the end of the sequence.
\end{methoddesc}
\begin{methoddesc}[mapping object]{__setitem__}{self, key, value}
@ -1101,14 +1108,17 @@ Called to implement assignment to \code{\var{self}[\var{key}]}. Same
note as for \method{__getitem__()}. This should only be implemented
for mappings if the objects support changes to the values for keys, or
if new keys can be added, or for sequences if elements can be
replaced.
replaced. The same exceptions should be raised for improper
\var{key} values as for the \method{__getitem__()} method.
\end{methoddesc}
\begin{methoddesc}[mapping object]{__delitem__}{self, key}
Called to implement deletion of \code{\var{self}[\var{key}]}. Same
note as for \method{__getitem__()}. This should only be implemented
for mappings if the objects support removal of keys, or for sequences
if elements can be removed from the sequence.
if elements can be removed from the sequence. The same exceptions
should be raised for improper \var{key} values as for the
\method{__getitem__()} method.
\end{methoddesc}