diff options
Diffstat (limited to 'Doc')
| -rw-r--r-- | Doc/lib/libre.tex | 35 |
1 files changed, 18 insertions, 17 deletions
diff --git a/Doc/lib/libre.tex b/Doc/lib/libre.tex index 1fba741..0ee2ba2 100644 --- a/Doc/lib/libre.tex +++ b/Doc/lib/libre.tex @@ -24,7 +24,7 @@ usage of the same character for the same purpose in string literals; for example, to match a literal backslash, one might have to write \code{'\e\e\e\e'} as the pattern string, because the regular expression must be \samp{\e\e}, and each backslash must be expressed as -\samp{\e\e} inside a regular Python string literal. +\samp{\e\e} inside a regular Python string literal. The solution is to use Python's raw string notation for regular expression patterns; backslashes are not handled in any special way in @@ -178,8 +178,8 @@ will match any lowercase letter, and \code{[a-zA-Z0-9]} matches any letter or digit. Character classes such as \code{\e w} or \code{\e S} (defined below) are also acceptable inside a range. If you want to include a \character{]} or a \character{-} inside a set, precede it with a -backslash, or place it as the first character. The -pattern \regexp{[]]} will match \code{']'}, for example. +backslash, or place it as the first character. The +pattern \regexp{[]]} will match \code{']'}, for example. You can match the characters not within a range by \dfn{complementing} the set. This is indicated by including a \character{\^} as the first @@ -209,7 +209,7 @@ inside a character class: \regexp{[(] [)]}. \item[\code{(?...)}] This is an extension notation (a \character{?} following a \character{(} is not meaningful otherwise). The first -character after the \character{?} +character after the \character{?} determines what the meaning and further syntax of the construct is. Extensions usually do not create a new group; \regexp{(?P<\var{name}>...)} is the only exception to this rule. @@ -231,13 +231,14 @@ the flag, the results are undefined. \item[\code{(?:...)}] A non-grouping version of regular parentheses. Matches whatever regular expression is inside the parentheses, but the -substring matched by the +substring matched by the group \emph{cannot} be retrieved after performing a match or -referenced later in the pattern. +referenced later in the pattern. \item[\code{(?P<\var{name}>...)}] Similar to regular parentheses, but the substring matched by the group is accessible via the symbolic group -name \var{name}. Group names must be valid Python identifiers. A +name \var{name}. Group names must be valid Python identifiers, and +each group name must be defined only once within a regular expression. A symbolic group is also a numbered group, just as if the group were not named. So the group named 'id' in the example above can also be referenced as the numbered group 1. @@ -292,7 +293,7 @@ resulting RE will match the second character. For example, \item[\code{\e \var{number}}] Matches the contents of the group of the same number. Groups are numbered starting from 1. For example, \regexp{(.+) \e 1} matches \code{'the the'} or \code{'55 55'}, but not -\code{'the end'} (note +\code{'the end'} (note the space after the group). This special sequence can only be used to match one of the first 99 groups. If the first digit of \var{number} is 0, or \var{number} is 3 octal digits long, it will not be interpreted @@ -300,7 +301,7 @@ as a group match, but as the character with octal value \var{number}. (There is a group 0, which is the entire matched pattern, but it can't be referenced with \regexp{\e 0}; instead, use \regexp{\e g<0>}.) Inside the \character{[} and \character{]} of a character class, all numeric -escapes are treated as characters. +escapes are treated as characters. \item[\code{\e A}] Matches only at the start of the string. @@ -387,7 +388,7 @@ The module defines the following functions and constants, and an exception: \begin{funcdesc}{compile}{pattern\optional{, flags}} Compile a regular expression pattern into a regular expression object, which can be used for matching using its \function{match()} and - \function{search()} methods, described below. + \function{search()} methods, described below. The expression's behaviour can be modified by specifying a \var{flags} value. Values can be any of the following variables, @@ -424,7 +425,7 @@ current locale. \begin{datadesc}{L} \dataline{LOCALE} Make \regexp{\e w}, \regexp{\e W}, \regexp{\e b}, and -\regexp{\e B} dependent on the current locale. +\regexp{\e B} dependent on the current locale. \end{datadesc} \begin{datadesc}{M} @@ -456,7 +457,7 @@ Make \regexp{\e w}, \regexp{\e W}, \regexp{\e b}, and \begin{datadesc}{X} \dataline{VERBOSE} This flag allows you to write regular expressions that look nicer. -Whitespace within the pattern is ignored, +Whitespace within the pattern is ignored, except when in a character class or preceded by an unescaped backslash, and, when a line contains a \character{\#} neither in a character class or preceded by an unescaped backslash, all characters @@ -605,7 +606,7 @@ attributes: corresponding \class{MatchObject} instance. Return \code{None} if no position in the string matches the pattern; note that this is different from finding a zero-length match at some point in the string. - + The optional \var{pos} and \var{endpos} parameters have the same meaning as for the \method{match()} method. \end{methoddesc} @@ -659,7 +660,7 @@ The flags argument used when the RE object was compiled, or \end{memberdesc} \begin{memberdesc}[RegexObject]{groupindex} -A dictionary mapping any symbolic group names defined by +A dictionary mapping any symbolic group names defined by \regexp{(?P<\var{id}>)} to group numbers. The dictionary is empty if no symbolic groups were used in the pattern. \end{memberdesc} @@ -695,13 +696,13 @@ the string matching the the corresponding parenthesized group. If a group number is negative or larger than the number of groups defined in the pattern, an \exception{IndexError} exception is raised. If a group is contained in a part of the pattern that did not match, -the corresponding result is \code{None}. If a group is contained in a +the corresponding result is \code{None}. If a group is contained in a part of the pattern that matched multiple times, the last match is returned. If the regular expression uses the \regexp{(?P<\var{name}>...)} syntax, the \var{groupN} arguments may also be strings identifying groups by -their group name. If a string argument is not used as a group name in +their group name. If a string argument is not used as a group name in the pattern, an \exception{IndexError} exception is raised. A moderately complicated example: @@ -765,7 +766,7 @@ Note that if \var{group} did not contribute to the match, this is \begin{memberdesc}[MatchObject]{pos} The value of \var{pos} which was passed to the \function{search()} or \function{match()} function. This is the index -into the string at which the RE engine started looking for a match. +into the string at which the RE engine started looking for a match. \end{memberdesc} \begin{memberdesc}[MatchObject]{endpos} |