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diff --git a/Doc/lib/libre.tex b/Doc/lib/libre.tex index 7100753..dc4ca2e 100644 --- a/Doc/lib/libre.tex +++ b/Doc/lib/libre.tex @@ -792,3 +792,59 @@ The regular expression object whose \method{match()} or \begin{memberdesc}[MatchObject]{string} The string passed to \function{match()} or \function{search()}. \end{memberdesc} + +\subsection{Examples} + +%\begin{list}{}{\leftmargin 0.7in \labelwidth 0.65in} + +%\item[Simulating scanf] + +\leftline{\strong{Simulating \cfunction{scanf()}}} + +Python does not currently have an equivalent to \cfunction{scanf()}. +\ttindex{scanf()} +Regular expressions are generally more powerful, though also more +verbose, than \cfunction{scanf()} format strings. The table below +offers some more-or-less equivalent mappings between +\cfunction{scanf()} format tokens and regular expressions. + +\begin{tableii}{l|l}{textrm}{\cfunction{scanf()} Token}{Regular Expression} + \lineii{\code{\%c}} + {\regexp{.}} + \lineii{\code{\%5c}} + {\regexp{.\{5\}}} + \lineii{\code{\%d}} + {\regexp{[-+]\e d+}} + \lineii{\code{\%e}, \code{\%E}, \code{\%f}, \code{\%g}} + {\regexp{[-+](\e d+(\e.\e d*)?|\e d*\e.\e d+)([eE]\e d+)?}} + \lineii{\code{\%i}} + {\regexp{[-+](0[xX][\e dA-Fa-f]+|0[0-7]*|\e d+)}} + \lineii{\code{\%o}} + {\regexp{0[0-7]*}} + \lineii{\code{\%s}} + {\regexp{[\textasciicircum\e s]+}} + \lineii{\code{\%u}} + {\regexp{\e d+}} + \lineii{\code{\%x}, \code{\%X}} + {\regexp{0[xX][\e dA-Fa-f]}} +\end{tableii} + +To extract the filename and numbers from a string like + +\begin{verbatim} + /usr/sbin/sendmail - 0 errors, 4 warnings +\end{verbatim} + +you would use a \cfunction{scanf()} format like + +\begin{verbatim} + %s - %d errors, %d warnings +\end{verbatim} + +The equivalent regular expression would be + +\begin{verbatim} + ([^\s]+) - (\d+) errors, (\d+) warnings +\end{verbatim} + +%\end{list} |