Explain the advantages of reversed.

This commit is contained in:
Raymond Hettinger 2003-11-12 16:39:30 +00:00
parent 607c00f792
commit bc3cba2881
1 changed files with 6 additions and 3 deletions

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@ -34,7 +34,7 @@ and returns an iterator that returns the elements of the sequence
in reverse order. in reverse order.
\begin{verbatim} \begin{verbatim}
>>> for i in reversed([1,2,3]): >>> for i in reversed(xrange(1,4)):
... print i ... print i
... ...
3 3
@ -42,9 +42,12 @@ in reverse order.
1 1
\end{verbatim} \end{verbatim}
Compared to extended slicing, \code{range(1,4)[::-1]}, \function{reversed()}
is easier to read, runs faster, and uses substantially less memory.
Note that \function{reversed()} only accepts sequences, not arbitrary Note that \function{reversed()} only accepts sequences, not arbitrary
iterators. If you want to reverse an iterator, convert it to iterators. If you want to reverse an iterator, first convert it to
a list or tuple with \function{list()} or \function{tuple()}. a list with \function{list()}.
\begin{verbatim} \begin{verbatim}
>>> input = open('/etc/passwd', 'r') >>> input = open('/etc/passwd', 'r')