Doc/lib/libregsub.tex

   1 \section{\module{regsub} ---
   2          String operations using regular expressions}
   3
   4 \declaremodule{standard}{regsub}
   5 \modulesynopsis{Substitution and splitting operations that use
   6                 regular expressions.  \strong{Obsolete!}}
   7
   8
   9 This module defines a number of functions useful for working with
  10 regular expressions (see built-in module \refmodule{regex}).
  11
  12 Warning: these functions are not thread-safe.
  13
  14 \strong{Obsolescence note:}
  15 This module is obsolete as of Python version 1.5; it is still being
  16 maintained because much existing code still uses it.  All new code in
  17 need of regular expressions should use the new \refmodule{re} module, which
  18 supports the more powerful and regular Perl-style regular expressions.
  19 Existing code should be converted.  The standard library module
  20 \module{reconvert} helps in converting \refmodule{regex} style regular
  21 expressions to \refmodule{re} style regular expressions.  (For more
  22 conversion help, see Andrew Kuchling's\index{Kuchling, Andrew}
  23 ``regex-to-re HOWTO'' at
  24 \url{http://www.python.org/doc/howto/regex-to-re/}.)
  25
  26
  27 \begin{funcdesc}{sub}{pat, repl, str}
  28 Replace the first occurrence of pattern \var{pat} in string
  29 \var{str} by replacement \var{repl}.  If the pattern isn't found,
  30 the string is returned unchanged.  The pattern may be a string or an
  31 already compiled pattern.  The replacement may contain references
  32 \samp{\e \var{digit}} to subpatterns and escaped backslashes.
  33 \end{funcdesc}
  34
  35 \begin{funcdesc}{gsub}{pat, repl, str}
  36 Replace all (non-overlapping) occurrences of pattern \var{pat} in
  37 string \var{str} by replacement \var{repl}.  The same rules as for
  38 \code{sub()} apply.  Empty matches for the pattern are replaced only
  39 when not adjacent to a previous match, so e.g.
  40 \code{gsub('', '-', 'abc')} returns \code{'-a-b-c-'}.
  41 \end{funcdesc}
  42
  43 \begin{funcdesc}{split}{str, pat\optional{, maxsplit}}
  44 Split the string \var{str} in fields separated by delimiters matching
  45 the pattern \var{pat}, and return a list containing the fields.  Only
  46 non-empty matches for the pattern are considered, so e.g.
  47 \code{split('a:b', ':*')} returns \code{['a', 'b']} and
  48 \code{split('abc', '')} returns \code{['abc']}.  The \var{maxsplit}
  49 defaults to 0. If it is nonzero, only \var{maxsplit} number of splits
  50 occur, and the remainder of the string is returned as the final
  51 element of the list.
  52 \end{funcdesc}
  53
  54 \begin{funcdesc}{splitx}{str, pat\optional{, maxsplit}}
  55 Split the string \var{str} in fields separated by delimiters matching
  56 the pattern \var{pat}, and return a list containing the fields as well
  57 as the separators.  For example, \code{splitx('a:::b', ':*')} returns
  58 \code{['a', ':::', 'b']}.  Otherwise, this function behaves the same
  59 as \code{split}.
  60 \end{funcdesc}
  61
  62 \begin{funcdesc}{capwords}{s\optional{, pat}}
  63 Capitalize words separated by optional pattern \var{pat}.  The default
  64 pattern uses any characters except letters, digits and underscores as
  65 word delimiters.  Capitalization is done by changing the first
  66 character of each word to upper case.
  67 \end{funcdesc}
  68
  69 \begin{funcdesc}{clear_cache}{}
  70 The regsub module maintains a cache of compiled regular expressions,
  71 keyed on the regular expression string and the syntax of the regex
  72 module at the time the expression was compiled.  This function clears
  73 that cache.
  74 \end{funcdesc}