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
parent
391564f10f
commit
e9625e86b8
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@ -153,6 +153,8 @@ class: \code{[(] [)]}.
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\item[\code{(?...)}] This is an extension notation (a '?' following a
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'(' is not meaningful otherwise). The first character after the '?'
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determines what the meaning and further syntax of the construct is.
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Extensions usually do not create a new group;
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\code{(?P<\var{name}>...)} is the only exception to this rule.
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Following are the currently supported extensions.
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%
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\item[\code{(?iLmsx)}] (One or more letters from the set \samp{i},
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@ -160,16 +162,16 @@ Following are the currently supported extensions.
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the empty string; the letters set the corresponding flags
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(\constant{re.I}, \constant{re.L}, \constant{re.M}, \constant{re.S},
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\constant{re.X}) for the entire regular expression. This is useful if
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you wish include the flags as part of the regular expression, instead
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you wish to include the flags as part of the regular expression, instead
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of passing a \var{flag} argument to the \function{compile()} function.
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%
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\item[\code{(?:...)}] A non-grouping version of regular parentheses.
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Matches whatever's inside the parentheses, but the text matched by the
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Matches whatever's inside the parentheses, but the substring matched by the
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group \emph{cannot} be retrieved after performing a match or
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referenced later in the pattern.
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%
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\item[\code{(?P<\var{name}>...)}] Similar to regular parentheses, but
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the text matched by the group is accessible via the symbolic group
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the substring matched by the group is accessible via the symbolic group
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name \var{name}. Group names must be valid Python identifiers. A
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symbolic group is also a numbered group, just as if the group were not
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named. So the group named 'id' in the example above can also be
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@ -214,6 +216,8 @@ the space after the group). This special sequence can only be used to
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match one of the first 99 groups. If the first digit of \var{number}
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is 0, or \var{number} is 3 octal digits long, it will not be interpreted
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as a group match, but as the character with octal value \var{number}.
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Inside the \code{[} and \code{]} of a character class, all numeric
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escapes are treated as characters.
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%
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\item[\code{\e A}] Matches only at the start of the string.
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%
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@ -300,7 +304,7 @@ newline (if any) at the end of the string.
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\begin{datadesc}{S}
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\dataline{DOTALL}
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Make the \code{.} special character any character at all, including a
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Make the \code{.} special character match any character at all, including a
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newline; without this flag, \code{.} will match anything \emph{except}
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a newline.
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\end{datadesc}
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@ -393,8 +397,8 @@ replacement string. For example:
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%
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\begin{verbatim}
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>>> def dashrepl(matchobj):
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... if matchobj.group(0) == '-': return ' '
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... else: return '-'
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.... if matchobj.group(0) == '-': return ' '
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.... else: return '-'
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>>> re.sub('-{1,2}', dashrepl, 'pro----gram-files')
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'pro--gram files'
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\end{verbatim}
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@ -411,6 +415,21 @@ the default value of 0 means to replace all occurrences.
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Empty matches for the pattern are replaced only when not adjacent to a
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previous match, so \samp{sub('x*', '-', 'abc')} returns \code{'-a-b-c-'}.
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If \var{repl} is a string, any backslash escapes in it are processed.
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That is, \samp{\e n} is converted to a single newline character,
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\samp{\e r} is converted to a linefeed, and so forth. Unknown escapes
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such as \samp{\e j} are XXX. Backreferences, such as \samp{\e 6} are
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replaced with the substring matched by group 6 in the pattern.
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In addition to character escapes and backreferences as described
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above, \samp{\e g<name>} will use the substring matched by the group
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named \samp{name}, as defined by the \samp{(?P<name>...)} syntax.
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\samp{\e g<number>} uses the corresponding group number; \samp{\e
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g<2>} is therefore equivalent to \samp{\e 2}, but isn't ambiguous in a
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replacement such as \samp{\e g<2>0}. \samp{\e 20} would be
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interpreted as a reference to group 20, not a reference to group 2
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followed by the literal character \samp{0}.
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\end{funcdesc}
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\begin{funcdesc}{subn}{pattern, repl, string\optional{, count\code{ = 0}}}
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@ -153,6 +153,8 @@ class: \code{[(] [)]}.
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\item[\code{(?...)}] This is an extension notation (a '?' following a
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'(' is not meaningful otherwise). The first character after the '?'
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determines what the meaning and further syntax of the construct is.
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Extensions usually do not create a new group;
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\code{(?P<\var{name}>...)} is the only exception to this rule.
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Following are the currently supported extensions.
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%
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\item[\code{(?iLmsx)}] (One or more letters from the set \samp{i},
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@ -160,16 +162,16 @@ Following are the currently supported extensions.
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the empty string; the letters set the corresponding flags
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(\constant{re.I}, \constant{re.L}, \constant{re.M}, \constant{re.S},
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\constant{re.X}) for the entire regular expression. This is useful if
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you wish include the flags as part of the regular expression, instead
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you wish to include the flags as part of the regular expression, instead
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of passing a \var{flag} argument to the \function{compile()} function.
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%
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\item[\code{(?:...)}] A non-grouping version of regular parentheses.
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Matches whatever's inside the parentheses, but the text matched by the
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Matches whatever's inside the parentheses, but the substring matched by the
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group \emph{cannot} be retrieved after performing a match or
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referenced later in the pattern.
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%
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\item[\code{(?P<\var{name}>...)}] Similar to regular parentheses, but
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the text matched by the group is accessible via the symbolic group
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the substring matched by the group is accessible via the symbolic group
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name \var{name}. Group names must be valid Python identifiers. A
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symbolic group is also a numbered group, just as if the group were not
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named. So the group named 'id' in the example above can also be
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@ -214,6 +216,8 @@ the space after the group). This special sequence can only be used to
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match one of the first 99 groups. If the first digit of \var{number}
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is 0, or \var{number} is 3 octal digits long, it will not be interpreted
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as a group match, but as the character with octal value \var{number}.
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Inside the \code{[} and \code{]} of a character class, all numeric
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escapes are treated as characters.
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%
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\item[\code{\e A}] Matches only at the start of the string.
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%
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@ -300,7 +304,7 @@ newline (if any) at the end of the string.
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\begin{datadesc}{S}
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\dataline{DOTALL}
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Make the \code{.} special character any character at all, including a
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Make the \code{.} special character match any character at all, including a
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newline; without this flag, \code{.} will match anything \emph{except}
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a newline.
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\end{datadesc}
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@ -393,8 +397,8 @@ replacement string. For example:
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%
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\begin{verbatim}
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>>> def dashrepl(matchobj):
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... if matchobj.group(0) == '-': return ' '
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... else: return '-'
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.... if matchobj.group(0) == '-': return ' '
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.... else: return '-'
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>>> re.sub('-{1,2}', dashrepl, 'pro----gram-files')
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'pro--gram files'
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\end{verbatim}
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@ -411,6 +415,21 @@ the default value of 0 means to replace all occurrences.
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Empty matches for the pattern are replaced only when not adjacent to a
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previous match, so \samp{sub('x*', '-', 'abc')} returns \code{'-a-b-c-'}.
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If \var{repl} is a string, any backslash escapes in it are processed.
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That is, \samp{\e n} is converted to a single newline character,
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\samp{\e r} is converted to a linefeed, and so forth. Unknown escapes
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such as \samp{\e j} are XXX. Backreferences, such as \samp{\e 6} are
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replaced with the substring matched by group 6 in the pattern.
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In addition to character escapes and backreferences as described
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above, \samp{\e g<name>} will use the substring matched by the group
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named \samp{name}, as defined by the \samp{(?P<name>...)} syntax.
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\samp{\e g<number>} uses the corresponding group number; \samp{\e
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g<2>} is therefore equivalent to \samp{\e 2}, but isn't ambiguous in a
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replacement such as \samp{\e g<2>0}. \samp{\e 20} would be
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interpreted as a reference to group 20, not a reference to group 2
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followed by the literal character \samp{0}.
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\end{funcdesc}
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\begin{funcdesc}{subn}{pattern, repl, string\optional{, count\code{ = 0}}}
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