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
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
\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.
\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.
\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
(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.
\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,
\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}
\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
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}
\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}
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:
\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}
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