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AMK's version from the latest pypcre distribution. This clarifies a 

few things and adds docs for what happens to escapes in replacement
strings.
This commit is contained in:
Guido van Rossum 1998-04-02 01:32:24 +00:00
parent 391564f10f
commit e9625e86b8
2 changed files with 50 additions and 12 deletions
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31
Doc/lib/libre.tex
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@ -153,6 +153,8 @@ class: \code{[(] [)]}.
\item[\code{(?...)}] This is an extension notation (a '?' following a \item[\code{(?...)}] This is an extension notation (a '?' following a
'(' is not meaningful otherwise). The first character after the '?' '(' is not meaningful otherwise). The first character after the '?'
determines what the meaning and further syntax of the construct is. 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. Following are the currently supported extensions.
% %
\item[\code{(?iLmsx)}] (One or more letters from the set \samp{i}, \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 the empty string; the letters set the corresponding flags
(\constant{re.I}, \constant{re.L}, \constant{re.M}, \constant{re.S}, (\constant{re.I}, \constant{re.L}, \constant{re.M}, \constant{re.S},
\constant{re.X}) for the entire regular expression. This is useful if \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. of passing a \var{flag} argument to the \function{compile()} function.
% %
\item[\code{(?:...)}] A non-grouping version of regular parentheses. \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 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 \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 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 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 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} 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 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}. 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. \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} \begin{datadesc}{S}
\dataline{DOTALL} \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} newline; without this flag, \code{.} will match anything \emph{except}
a newline. a newline.
\end{datadesc} \end{datadesc}
@ -393,8 +397,8 @@ replacement string. For example:
% %
\begin{verbatim} \begin{verbatim}
>>> def dashrepl(matchobj): >>> def dashrepl(matchobj):
... if matchobj.group(0) == '-': return ' ' .... if matchobj.group(0) == '-': return ' '
... else: return '-' .... else: return '-'
>>> re.sub('-{1,2}', dashrepl, 'pro----gram-files') >>> re.sub('-{1,2}', dashrepl, 'pro----gram-files')
'pro--gram files' 'pro--gram files'
\end{verbatim} \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 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-'}. 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} \end{funcdesc}
\begin{funcdesc}{subn}{pattern, repl, string\optional{, count\code{ = 0}}} \begin{funcdesc}{subn}{pattern, repl, string\optional{, count\code{ = 0}}}

31
Doc/libre.tex
View File

@ -153,6 +153,8 @@ class: \code{[(] [)]}.
\item[\code{(?...)}] This is an extension notation (a '?' following a \item[\code{(?...)}] This is an extension notation (a '?' following a
'(' is not meaningful otherwise). The first character after the '?' '(' is not meaningful otherwise). The first character after the '?'
determines what the meaning and further syntax of the construct is. 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. Following are the currently supported extensions.
% %
\item[\code{(?iLmsx)}] (One or more letters from the set \samp{i}, \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 the empty string; the letters set the corresponding flags
(\constant{re.I}, \constant{re.L}, \constant{re.M}, \constant{re.S}, (\constant{re.I}, \constant{re.L}, \constant{re.M}, \constant{re.S},
\constant{re.X}) for the entire regular expression. This is useful if \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. of passing a \var{flag} argument to the \function{compile()} function.
% %
\item[\code{(?:...)}] A non-grouping version of regular parentheses. \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 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 \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 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 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 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} 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 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}. 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. \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} \begin{datadesc}{S}
\dataline{DOTALL} \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} newline; without this flag, \code{.} will match anything \emph{except}
a newline. a newline.
\end{datadesc} \end{datadesc}
@ -393,8 +397,8 @@ replacement string. For example:
% %
\begin{verbatim} \begin{verbatim}
>>> def dashrepl(matchobj): >>> def dashrepl(matchobj):
... if matchobj.group(0) == '-': return ' ' .... if matchobj.group(0) == '-': return ' '
... else: return '-' .... else: return '-'
>>> re.sub('-{1,2}', dashrepl, 'pro----gram-files') >>> re.sub('-{1,2}', dashrepl, 'pro----gram-files')
'pro--gram files' 'pro--gram files'
\end{verbatim} \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 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-'}. 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} \end{funcdesc}
\begin{funcdesc}{subn}{pattern, repl, string\optional{, count\code{ = 0}}} \begin{funcdesc}{subn}{pattern, repl, string\optional{, count\code{ = 0}}}