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Some clarifications on operations for mapping types, based on comments 

from Gerry Weiner <gerry@ucar.edu>.
This commit is contained in:
Fred Drake 1999-06-10 22:37:34 +00:00
parent 697c779d98
commit 9c5cc14d23
1 changed files with 36 additions and 20 deletions
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Doc/lib/libstdtypes.tex
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@ -539,23 +539,9 @@ Dictionaries are created by placing a comma-separated list of
\code{\{'jack': 4098, 'sjoerd': 4127\}} or
\code{\{4098: 'jack', 4127: 'sjoerd'\}}.
The following operations are defined on mappings (where \var{a} is a
mapping, \var{k} is a key and \var{x} is an arbitrary object):
\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}] = \var{x}}{set \code{\var{a}[\var{k}]} to \var{x}}{}
\lineiii{del \var{a}[\var{k}]}{remove \code{\var{a}[\var{k}]} from \var{a}}{(1)}
\lineiii{\var{a}.clear()}{remove all items from \code{a}}{}
\lineiii{\var{a}.copy()}{a (shallow) copy of \code{a}}{}
\lineiii{\var{a}.has_key(\var{k})}{\code{1} if \var{a} has a key \var{k}, else \code{0}}{}
\lineiii{\var{a}.items()}{a copy of \var{a}'s list of (\var{key}, \var{value}) pairs}{(2)}
\lineiii{\var{a}.keys()}{a copy of \var{a}'s list of keys}{(2)}
\lineiii{\var{a}.update(\var{b})}{\code{for k, v in \var{b}.items(): \var{a}[k] = v}}{(3)}
\lineiii{\var{a}.values()}{a copy of \var{a}'s list of values}{(2)}
\lineiii{\var{a}.get(\var{k}\optional{, \var{f}})}{the value of \var{a} with key \var{k}}{(4)}
\end{tableiii}
The following operations are defined on mappings (where \var{a} and
\var{b} are mappings, \var{k} is a key, and \var{v} and \var{x} are
arbitrary objects):
\indexiii{operations on}{mapping}{types}
\indexiii{operations on}{dictionary}{type}
\stindex{del}
@ -569,18 +555,48 @@ mapping, \var{k} is a key and \var{x} is an arbitrary object):
\ttindex{update()}
\ttindex{values()}
\ttindex{get()}}
\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}] = \var{x}}
{set \code{\var{a}[\var{k}]} to \var{x}}
{}
\lineiii{del \var{a}[\var{k}]}
{remove \code{\var{a}[\var{k}]} from \var{a}}
{(1)}
\lineiii{\var{a}.clear()}{remove all items from \code{a}}{}
\lineiii{\var{a}.copy()}{a (shallow) copy of \code{a}}{}
\lineiii{\var{a}.has_key(\var{k})}
{\code{1} if \var{a} has a key \var{k}, else \code{0}}
{}
\lineiii{\var{a}.items()}
{a copy of \var{a}'s list of (\var{key}, \var{value}) pairs}
{(2)}
\lineiii{\var{a}.keys()}{a copy of \var{a}'s list of keys}{(2)}
\lineiii{\var{a}.update(\var{b})}
{\code{for k, v in \var{b}.items(): \var{a}[k] = v}}
{(3)}
\lineiii{\var{a}.values()}{a copy of \var{a}'s list of values}{(2)}
\lineiii{\var{a}.get(\var{k}\optional{, \var{x}})}
{\code{\var{a}[\var{k}]} if \code{\var{a}.has_key(\var{k})},
else \var{x}}
{(4)}
\end{tableiii}
\noindent
Notes:
\begin{description}
\item[(1)] Raises an exception if \var{k} is not in the map.
\item[(1)] Raises a \exception{KeyError} exception if \var{k} is not
in the map.
\item[(2)] Keys and values are listed in random order.
\item[(3)] \var{b} must be of the same type as \var{a}.
\item[(4)] Never raises an exception if \var{k} is not in the map,
instead it returns \var{f}. \var{f} is optional, when not provided
and \var{k} is not in the map, \code{None} is returned.
instead it returns \var{f}. \var{f} is optional; when \var{f} is not
provided and \var{k} is not in the map, \code{None} is returned.
\end{description}