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Commit 7ceb29e4 authored by Raymond Hettinger's avatar Raymond Hettinger
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Incorporate documentation suggestions from feedback on comp.lang.python. 

* Positive wording for the description of why < and > and = can all
  be False.

* Move to a three column table format that puts long method names
  side-by-side with their operator equivalents

* Mention that KeyError can be raised by Set.pop() and Set.remove().

* Minor tweaks to the examples.

Will backport as soon as Fred rebuilds the docs so I can confirm
the tables formatted properly
parent ee562fc0
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Showing with 42 additions and 55 deletions
Doc/lib/libsets.tex
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......@@ -65,41 +65,31 @@ elements must be known when the constructor is called.
Instances of \class{Set} and \class{ImmutableSet} both provide
the following operations:
\begin{tableii}{c|l}{code}{Operation}{Result}
\lineii{len(\var{s})}{cardinality of set \var{s}}
\begin{tableiii}{c|c|l}{code}{Operation}{Equivalent}{Result}
\lineiii{len(\var{s})}{}{cardinality of set \var{s}}
\hline
\lineii{\var{x} in \var{s}}
\lineiii{\var{x} in \var{s}}{}
{test \var{x} for membership in \var{s}}
\lineii{\var{x} not in \var{s}}
\lineiii{\var{x} not in \var{s}}{}
{test \var{x} for non-membership in \var{s}}
\lineii{\var{s}.issubset(\var{t})}
{test whether every element in \var{s} is in \var{t};
\code{\var{s} <= \var{t}} is equivalent}
\lineii{\var{s}.issuperset(\var{t})}
{test whether every element in \var{t} is in \var{s};
\code{\var{s} >= \var{t}} is equivalent}
\lineiii{\var{s}.issubset(\var{t})}{\code{\var{s} <= \var{t}}}
{test whether every element in \var{s} is in \var{t}}
\lineiii{\var{s}.issuperset(\var{t})}{\code{\var{s} >= \var{t}}}
{test whether every element in \var{t} is in \var{s}}
\hline
\lineii{\var{s} | \var{t}}
{new set with elements from both \var{s} and \var{t}}
\lineii{\var{s}.union(\var{t})}
\lineiii{\var{s}.union(\var{t})}{\var{s} | \var{t}}
{new set with elements from both \var{s} and \var{t}}
\lineii{\var{s} \&\ \var{t}}
\lineiii{\var{s}.intersection(\var{t})}{\var{s} \&\ \var{t}}
{new set with elements common to \var{s} and \var{t}}
\lineii{\var{s}.intersection(\var{t})}
{new set with elements common to \var{s} and \var{t}}
\lineii{\var{s} - \var{t}}
{new set with elements in \var{s} but not in \var{t}}
\lineii{\var{s}.difference(\var{t})}
\lineiii{\var{s}.difference(\var{t})}{\var{s} - \var{t}}
{new set with elements in \var{s} but not in \var{t}}
\lineii{\var{s} \^\ \var{t}}
\lineiii{\var{s}.symmetric_difference(\var{t})}{\var{s} \^\ \var{t}}
{new set with elements in either \var{s} or \var{t} but not both}
\lineii{\var{s}.symmetric_difference(\var{t})}
{new set with elements in either \var{s} or \var{t} but not both}
\lineii{\var{s}.copy()}
\lineiii{\var{s}.copy()}{}
{new set with a shallow copy of \var{s}}
\end{tableii}
\end{tableiii}
In addition, both \class{Set} and \class{ImmutableSet}
support set to set comparisons. Two sets are equal if and only if
......@@ -112,8 +102,9 @@ superset of the second set (is a superset, but is not equal).
The subset and equality comparisons do not generalize to a complete
ordering function. For example, any two disjoint sets are not equal and
are not subsets of each other, so \emph{none} of the following are true:
\code{\var{a}<\var{b}}, \code{\var{a}==\var{b}}, or \code{\var{a}>\var{b}}.
are not subsets of each other, so \emph{all} of the following return
\code{False}: \code{\var{a}<\var{b}}, \code{\var{a}==\var{b}}, or
\code{\var{a}>\var{b}}.
Accordingly, sets do not implement the \method{__cmp__} method.
Since sets only define partial ordering (subset relationships), the output
......@@ -122,47 +113,43 @@ of the \method{list.sort()} method is undefined for lists of sets.
The following table lists operations available in \class{ImmutableSet}
but not found in \class{Set}:
\begin{tableii}{c|l|c}{code}{Operation}{Result}
\begin{tableii}{c|l}{code}{Operation}{Result}
\lineii{hash(\var{s})}{returns a hash value for \var{s}}
\end{tableii}
The following table lists operations available in \class{Set}
but not found in \class{ImmutableSet}:
\begin{tableii}{c|l}{code}{Operation}{Result}
\lineii{\var{s} |= \var{t}}
{return set \var{s} with elements added from \var{t}}
\lineii{\var{s}.union_update(\var{t})}
\begin{tableiii}{c|c|l}{code}{Operation}{Equivalent}{Result}
\lineiii{\var{s}.union_update(\var{t})}
{\var{s} |= \var{t}}
{return set \var{s} with elements added from \var{t}}
\lineii{\var{s} \&= \var{t}}
\lineiii{\var{s}.intersection_update(\var{t})}
{\var{s} \&= \var{t}}
{return set \var{s} keeping only elements also found in \var{t}}
\lineii{\var{s}.intersection_update(\var{t})}
{return set \var{s} keeping only elements also found in \var{t}}
\lineii{\var{s} -= \var{t}}
{return set \var{s} after removing elements found in \var{t}}
\lineii{\var{s}.difference_update(\var{t})}
\lineiii{\var{s}.difference_update(\var{t})}
{\var{s} -= \var{t}}
{return set \var{s} after removing elements found in \var{t}}
\lineii{\var{s} \textasciicircum= \var{t}}
{return set \var{s} with elements from \var{s} or \var{t}
but not both}
\lineii{\var{s}.symmetric_difference_update(\var{t})}
\lineiii{\var{s}.symmetric_difference_update(\var{t})}
{\var{s} \textasciicircum= \var{t}}
{return set \var{s} with elements from \var{s} or \var{t}
but not both}
\hline
\lineii{\var{s}.add(\var{x})}
\lineiii{\var{s}.add(\var{x})}{}
{add element \var{x} to set \var{s}}
\lineii{\var{s}.remove(\var{x})}
{remove \var{x} from set \var{s}}
\lineii{\var{s}.discard(\var{x})}
\lineiii{\var{s}.remove(\var{x})}{}
{remove \var{x} from set \var{s}; raises KeyError if not present}
\lineiii{\var{s}.discard(\var{x})}{}
{removes \var{x} from set \var{s} if present}
\lineii{\var{s}.pop()}
{remove and return an arbitrary element from \var{s}}
\lineii{\var{s}.update(\var{t})}
\lineiii{\var{s}.pop()}{}
{remove and return an arbitrary element from \var{s}; raises
KeyError if empty}
\lineiii{\var{s}.update(\var{t})}{}
{add elements from \var{t} to set \var{s}}
\lineii{\var{s}.clear()}
\lineiii{\var{s}.clear()}{}
{remove all elements from set \var{s}}
\end{tableii}
\end{tableiii}
\subsection{Example \label{set-example}}
......@@ -171,11 +158,11 @@ but not found in \class{ImmutableSet}:
>>> from sets import Set
>>> engineers = Set(['John', 'Jane', 'Jack', 'Janice'])
>>> programmers = Set(['Jack', 'Sam', 'Susan', 'Janice'])
>>> management = Set(['Jane', 'Jack', 'Susan', 'Zack'])
>>> employees = engineers | programmers | management # union
>>> engineering_management = engineers & programmers # intersection
>>> fulltime_management = management - engineers - programmers # difference
>>> engineers.add('Marvin') # add element
>>> managers = Set(['Jane', 'Jack', 'Susan', 'Zack'])
>>> employees = engineers | programmers | managers # union
>>> engineering_management = engineers & managers # intersection
>>> fulltime_management = managers - engineers - programmers # difference
>>> engineers.add('Marvin') # add element
>>> print engineers
Set(['Jane', 'Marvin', 'Janice', 'John', 'Jack'])
>>> employees.issuperset(engineers) # superset test
......
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