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Diffstat (limited to 'Doc')
| -rw-r--r-- | Doc/lib/libstdtypes.tex | 28 |
1 files changed, 25 insertions, 3 deletions
diff --git a/Doc/lib/libstdtypes.tex b/Doc/lib/libstdtypes.tex index 1a7b505..469b9d3 100644 --- a/Doc/lib/libstdtypes.tex +++ b/Doc/lib/libstdtypes.tex @@ -999,12 +999,34 @@ Notes: should return a negative, zero or positive number depending on whether the first argument is considered smaller than, equal to, or larger than the second argument. Note that this slows the sorting process - down considerably; e.g. to sort a list in reverse order it is much - faster to call method \method{sort()} followed by \method{reverse()} - than to use method \method{sort()} with a comparison function that + down considerably; for example to sort a list in reverse order it is much + faster to call \method{sort()} followed by \method{reverse()} + than to use \method{sort()} with a comparison function that reverses the ordering of the elements. Passing \constant{None} as the comparison function is semantically equivalent to calling \method{sort()} with no comparison function. + \versionchanged[Support for \code{None} as an equivalent to omitting + \var{cmpfunc} was added]{2.3} + + As an example of using the \var{cmpfunc} argument to the + \method{sort()} method, consider sorting a list of sequences by the + second element of that list: + +\begin{verbatim} +def mycmp(a, b): + return cmp(a[1], b[1]) + +mylist.sort(mycmp) +\end{verbatim} + + A more time-efficient approach for reasonably-sized data structures can + often be used: + +\begin{verbatim} +tmplist = [(x[1], x) for x in mylist] +tmplist.sort() +mylist = [x for (key, x) in tmplist] +\end{verbatim} \item[(9)] Whether the \method{sort()} method is stable is not defined by the language (a sort is stable if it guarantees not to change the |