192 lines
6.7 KiB
TeX
192 lines
6.7 KiB
TeX
\section{Standard Module \sectcode{string}}
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\stmodindex{string}
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This module defines some constants useful for checking character
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classes and some useful string functions. See the modules
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\code{regex} and \code{regsub} for string functions based on regular
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expressions.
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The constants defined in this module are are:
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\renewcommand{\indexsubitem}{(data in module string)}
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\begin{datadesc}{digits}
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The string \code{'0123456789'}.
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\end{datadesc}
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\begin{datadesc}{hexdigits}
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The string \code{'0123456789abcdefABCDEF'}.
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\end{datadesc}
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\begin{datadesc}{letters}
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The concatenation of the strings \code{lowercase} and
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\code{uppercase} described below.
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\end{datadesc}
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\begin{datadesc}{lowercase}
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A string containing all the characters that are considered lowercase
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letters. On most systems this is the string
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\code{'abcdefghijklmnopqrstuvwxyz'}. Do not change its definition ---
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the effect on the routines \code{upper} and \code{swapcase} is
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undefined.
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\end{datadesc}
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\begin{datadesc}{octdigits}
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The string \code{'01234567'}.
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\end{datadesc}
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\begin{datadesc}{uppercase}
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A string containing all the characters that are considered uppercase
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letters. On most systems this is the string
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\code{'ABCDEFGHIJKLMNOPQRSTUVWXYZ'}. Do not change its definition ---
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the effect on the routines \code{lower} and \code{swapcase} is
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undefined.
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\end{datadesc}
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\begin{datadesc}{whitespace}
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A string containing all characters that are considered whitespace.
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On most systems this includes the characters space, tab, linefeed,
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return, formfeed, and vertical tab. Do not change its definition ---
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the effect on the routines \code{strip} and \code{split} is
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undefined.
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\end{datadesc}
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The functions defined in this module are:
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\renewcommand{\indexsubitem}{(in module string)}
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\begin{funcdesc}{atof}{s}
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Convert a string to a floating point number. The string must have
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the standard syntax for a floating point literal in Python, optionally
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preceded by a sign (\samp{+} or \samp{-}).
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\end{funcdesc}
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\begin{funcdesc}{atoi}{s\optional{\, base}}
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Convert string \var{s} to an integer in the given \var{base}. The
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string must consist of one or more digits, optionally preceded by a
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sign (\samp{+} or \samp{-}). The \var{base} defaults to 10. If it is
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0, a default base is chosen depending on the leading characters of the
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string (after stripping the sign): \samp{0x} or \samp{0X} means 16,
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\samp{0} means 8, anything else means 10. If \var{base} is 16, a
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leading \samp{0x} or \samp{0X} is always accepted. (Note: for a more
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flexible interpretation of numeric literals, use the built-in function
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\code{eval()}.)
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\bifuncindex{eval}
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\end{funcdesc}
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\begin{funcdesc}{atol}{s\optional{\, base}}
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Convert string \var{s} to a long integer in the given \var{base}. The
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string must consist of one or more digits, optionally preceded by a
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sign (\samp{+} or \samp{-}). The \var{base} argument has the same
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meaning as for \code{atoi()}. A trailing \samp{l} or \samp{L} is not
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allowed.
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\end{funcdesc}
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\begin{funcdesc}{expandtabs}{s\, tabsize}
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Expand tabs in a string, i.e.\ replace them by one or more spaces,
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depending on the current column and the given tab size. The column
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number is reset to zero after each newline occurring in the string.
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This doesn't understand other non-printing characters or escape
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sequences.
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\end{funcdesc}
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\begin{funcdesc}{find}{s\, sub\optional{\, start}}
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Return the lowest index in \var{s} not smaller than \var{start} where the
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substring \var{sub} is found. Return \code{-1} when \var{sub}
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does not occur as a substring of \var{s} with index at least \var{start}.
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If \var{start} is omitted, it defaults to \code{0}. If \var{start} is
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negative, \code{len(\var{s})} is added.
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\end{funcdesc}
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\begin{funcdesc}{rfind}{s\, sub\optional{\, start}}
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Like \code{find} but find the highest index.
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\end{funcdesc}
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\begin{funcdesc}{index}{s\, sub\optional{\, start}}
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Like \code{find} but raise \code{ValueError} when the substring is
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not found.
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\end{funcdesc}
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\begin{funcdesc}{rindex}{s\, sub\optional{\, start}}
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Like \code{rfind} but raise \code{ValueError} when the substring is
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not found.
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\end{funcdesc}
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\begin{funcdesc}{count}{s\, sub\optional{\, start}}
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Return the number of (non-overlapping) occurrences of substring
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\var{sub} in string \var{s} with index at least \var{start}.
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If \var{start} is omitted, it defaults to \code{0}. If \var{start} is
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negative, \code{len(\var{s})} is added.
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\end{funcdesc}
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\begin{funcdesc}{lower}{s}
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Convert letters to lower case.
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\end{funcdesc}
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\begin{funcdesc}{split}{s}
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Return a list of the whitespace-delimited words of the string
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\var{s}.
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\end{funcdesc}
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\begin{funcdesc}{splitfields}{s\, sep}
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Return a list containing the fields of the string \var{s}, using
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the string \var{sep} as a separator. The list will have one more
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items than the number of non-overlapping occurrences of the
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separator in the string. Thus, \code{string.splitfields(\var{s}, '
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')} is not the same as \code{string.split(\var{s})}, as the latter
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only returns non-empty words. As a special case,
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\code{splitfields(\var{s}, '')} returns \code{[\var{s}]}, for any string
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\var{s}. (See also \code{regsub.split()}.)
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\end{funcdesc}
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\begin{funcdesc}{join}{words}
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Concatenate a list or tuple of words with intervening spaces.
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\end{funcdesc}
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\begin{funcdesc}{joinfields}{words\, sep}
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Concatenate a list or tuple of words with intervening separators.
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It is always true that
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\code{string.joinfields(string.splitfields(\var{t}, \var{sep}), \var{sep})}
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equals \var{t}.
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\end{funcdesc}
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\begin{funcdesc}{strip}{s}
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Remove leading and trailing whitespace from the string
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\var{s}.
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\end{funcdesc}
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\begin{funcdesc}{swapcase}{s}
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Convert lower case letters to upper case and vice versa.
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\end{funcdesc}
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\begin{funcdesc}{upper}{s}
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Convert letters to upper case.
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\end{funcdesc}
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\begin{funcdesc}{ljust}{s\, width}
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\funcline{rjust}{s\, width}
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\funcline{center}{s\, width}
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These functions respectively left-justify, right-justify and center a
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string in a field of given width.
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They return a string that is at least
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\var{width}
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characters wide, created by padding the string
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\var{s}
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with spaces until the given width on the right, left or both sides.
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The string is never truncated.
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\end{funcdesc}
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\begin{funcdesc}{zfill}{s\, width}
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Pad a numeric string on the left with zero digits until the given
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width is reached. Strings starting with a sign are handled correctly.
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\end{funcdesc}
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This module is implemented in Python. Much of its functionality has
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been reimplemented in the built-in module \code{strop}. However, you
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should \emph{never} import the latter module directly. When
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\code{string} discovers that \code{strop} exists, it transparently
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replaces parts of itself with the implementation from \code{strop}.
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After initialization, there is \emph{no} overhead in using
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\code{string} instead of \code{strop}.
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\bimodindex{strop}
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