diff options
Diffstat (limited to 'Doc')
| -rw-r--r-- | Doc/lib/libre.tex | 31 | ||||
| -rw-r--r-- | Doc/libre.tex | 31 |
2 files changed, 50 insertions, 12 deletions
diff --git a/Doc/lib/libre.tex b/Doc/lib/libre.tex index 85471e5..dbc94cc 100644 --- a/Doc/lib/libre.tex +++ b/Doc/lib/libre.tex @@ -153,6 +153,8 @@ class: \code{[(] [)]}. \item[\code{(?...)}] This is an extension notation (a '?' following a '(' is not meaningful otherwise). The first character after the '?' determines what the meaning and further syntax of the construct is. +Extensions usually do not create a new group; +\code{(?P<\var{name}>...)} is the only exception to this rule. Following are the currently supported extensions. % \item[\code{(?iLmsx)}] (One or more letters from the set \samp{i}, @@ -160,16 +162,16 @@ Following are the currently supported extensions. the empty string; the letters set the corresponding flags (\constant{re.I}, \constant{re.L}, \constant{re.M}, \constant{re.S}, \constant{re.X}) for the entire regular expression. This is useful if -you wish include the flags as part of the regular expression, instead +you wish to include the flags as part of the regular expression, instead of passing a \var{flag} argument to the \function{compile()} function. % \item[\code{(?:...)}] A non-grouping version of regular parentheses. -Matches whatever's inside the parentheses, but the text matched by the +Matches whatever's inside the parentheses, but the substring matched by the group \emph{cannot} be retrieved after performing a match or referenced later in the pattern. % \item[\code{(?P<\var{name}>...)}] Similar to regular parentheses, but -the text matched by the group is accessible via the symbolic group +the substring matched by the group is accessible via the symbolic group name \var{name}. Group names must be valid Python identifiers. 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 @@ -214,6 +216,8 @@ 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 as a group match, but as the character with octal value \var{number}. +Inside the \code{[} and \code{]} of a character class, all numeric +escapes are treated as characters. % \item[\code{\e A}] Matches only at the start of the string. % @@ -300,7 +304,7 @@ newline (if any) at the end of the string. \begin{datadesc}{S} \dataline{DOTALL} -Make the \code{.} special character any character at all, including a +Make the \code{.} special character match any character at all, including a newline; without this flag, \code{.} will match anything \emph{except} a newline. \end{datadesc} @@ -393,8 +397,8 @@ replacement string. For example: % \begin{verbatim} >>> def dashrepl(matchobj): -... if matchobj.group(0) == '-': return ' ' -... else: return '-' +.... if matchobj.group(0) == '-': return ' ' +.... else: return '-' >>> re.sub('-{1,2}', dashrepl, 'pro----gram-files') 'pro--gram files' \end{verbatim} @@ -411,6 +415,21 @@ the default value of 0 means to replace all occurrences. Empty matches for the pattern are replaced only when not adjacent to a previous match, so \samp{sub('x*', '-', 'abc')} returns \code{'-a-b-c-'}. + +If \var{repl} is a string, any backslash escapes in it are processed. +That is, \samp{\e n} is converted to a single newline character, +\samp{\e r} is converted to a linefeed, and so forth. Unknown escapes +such as \samp{\e j} are XXX. Backreferences, such as \samp{\e 6} are +replaced with the substring matched by group 6 in the pattern. + +In addition to character escapes and backreferences as described +above, \samp{\e g<name>} will use the substring matched by the group +named \samp{name}, as defined by the \samp{(?P<name>...)} syntax. +\samp{\e g<number>} uses the corresponding group number; \samp{\e +g<2>} is therefore equivalent to \samp{\e 2}, but isn't ambiguous in a +replacement such as \samp{\e g<2>0}. \samp{\e 20} would be +interpreted as a reference to group 20, not a reference to group 2 +followed by the literal character \samp{0}. \end{funcdesc} \begin{funcdesc}{subn}{pattern, repl, string\optional{, count\code{ = 0}}} diff --git a/Doc/libre.tex b/Doc/libre.tex index 85471e5..dbc94cc 100644 --- a/Doc/libre.tex +++ b/Doc/libre.tex @@ -153,6 +153,8 @@ class: \code{[(] [)]}. \item[\code{(?...)}] This is an extension notation (a '?' following a '(' is not meaningful otherwise). The first character after the '?' determines what the meaning and further syntax of the construct is. +Extensions usually do not create a new group; +\code{(?P<\var{name}>...)} is the only exception to this rule. Following are the currently supported extensions. % \item[\code{(?iLmsx)}] (One or more letters from the set \samp{i}, @@ -160,16 +162,16 @@ Following are the currently supported extensions. the empty string; the letters set the corresponding flags (\constant{re.I}, \constant{re.L}, \constant{re.M}, \constant{re.S}, \constant{re.X}) for the entire regular expression. This is useful if -you wish include the flags as part of the regular expression, instead +you wish to include the flags as part of the regular expression, instead of passing a \var{flag} argument to the \function{compile()} function. % \item[\code{(?:...)}] A non-grouping version of regular parentheses. -Matches whatever's inside the parentheses, but the text matched by the +Matches whatever's inside the parentheses, but the substring matched by the group \emph{cannot} be retrieved after performing a match or referenced later in the pattern. % \item[\code{(?P<\var{name}>...)}] Similar to regular parentheses, but -the text matched by the group is accessible via the symbolic group +the substring matched by the group is accessible via the symbolic group name \var{name}. Group names must be valid Python identifiers. 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 @@ -214,6 +216,8 @@ 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 as a group match, but as the character with octal value \var{number}. +Inside the \code{[} and \code{]} of a character class, all numeric +escapes are treated as characters. % \item[\code{\e A}] Matches only at the start of the string. % @@ -300,7 +304,7 @@ newline (if any) at the end of the string. \begin{datadesc}{S} \dataline{DOTALL} -Make the \code{.} special character any character at all, including a +Make the \code{.} special character match any character at all, including a newline; without this flag, \code{.} will match anything \emph{except} a newline. \end{datadesc} @@ -393,8 +397,8 @@ replacement string. For example: % \begin{verbatim} >>> def dashrepl(matchobj): -... if matchobj.group(0) == '-': return ' ' -... else: return '-' +.... if matchobj.group(0) == '-': return ' ' +.... else: return '-' >>> re.sub('-{1,2}', dashrepl, 'pro----gram-files') 'pro--gram files' \end{verbatim} @@ -411,6 +415,21 @@ the default value of 0 means to replace all occurrences. Empty matches for the pattern are replaced only when not adjacent to a previous match, so \samp{sub('x*', '-', 'abc')} returns \code{'-a-b-c-'}. + +If \var{repl} is a string, any backslash escapes in it are processed. +That is, \samp{\e n} is converted to a single newline character, +\samp{\e r} is converted to a linefeed, and so forth. Unknown escapes +such as \samp{\e j} are XXX. Backreferences, such as \samp{\e 6} are +replaced with the substring matched by group 6 in the pattern. + +In addition to character escapes and backreferences as described +above, \samp{\e g<name>} will use the substring matched by the group +named \samp{name}, as defined by the \samp{(?P<name>...)} syntax. +\samp{\e g<number>} uses the corresponding group number; \samp{\e +g<2>} is therefore equivalent to \samp{\e 2}, but isn't ambiguous in a +replacement such as \samp{\e g<2>0}. \samp{\e 20} would be +interpreted as a reference to group 20, not a reference to group 2 +followed by the literal character \samp{0}. \end{funcdesc} \begin{funcdesc}{subn}{pattern, repl, string\optional{, count\code{ = 0}}} |