The module defines these functions, and an exception:
- match (pattern, string)
-
Return how many characters at the beginning of string match
the regular expression pattern. Return -1 if the
string does not match the pattern (this is different from a
zero-length match!).
- search (pattern, string)
-
Return the first position in string that matches the regular
expression pattern. Return -1 if no position in the string
matches the pattern (this is different from a zero-length match
anywhere!).
- compile (pattern[, translate])
-
Compile a regular expression pattern into a regular expression
object, which can be used for matching using its match() and
search() methods, described below. The optional argument
translate, if present, must be a 256-character string
indicating how characters (both of the pattern and of the strings to
be matched) are translated before comparing them; the i-th
element of the string gives the translation for the character with
ASCII code i. This can be used to implement
case-insensitive matching; see the casefold data item below.
The sequence
prog = regex.compile(pat)
result = prog.match(str)
is equivalent to
result = regex.match(pat, str)
but the version using compile() is more efficient when multiple
regular expressions are used concurrently in a single program. (The
compiled version of the last pattern passed to regex.match() or
regex.search() is cached, so programs that use only a single
regular expression at a time needn't worry about compiling regular
expressions.)
- set_syntax (flags)
-
Set the syntax to be used by future calls to compile(),
match() and search(). (Already compiled expression
objects are not affected.) The argument is an integer which is the
OR of several flag bits. The return value is the previous value of
the syntax flags. Names for the flags are defined in the standard
module regex_syntax ; read the
file "regex_syntax.py" for more information.
- get_syntax ()
-
Returns the current value of the syntax flags as an integer.
- symcomp (pattern[, translate])
-
This is like compile(), but supports symbolic group names: if a
parenthesis-enclosed group begins with a group name in angular
brackets, e.g. '\(<id>[a-z][a-z0-9]*\)', the group can
be referenced by its name in arguments to the group() method of
the resulting compiled regular expression object, like this:
p.group('id'). Group names may contain alphanumeric characters
and '_' only.
- error
-
Exception raised when a string passed to one of the functions here
is not a valid regular expression (e.g., unmatched parentheses) or
when some other error occurs during compilation or matching. (It is
never an error if a string contains no match for a pattern.)
- casefold
-
A string suitable to pass as the translate argument to
compile() to map all upper case characters to their lowercase
equivalents.
Compiled regular expression objects support these methods:
- match (string[, pos])
-
Return how many characters at the beginning of string match
the compiled regular expression. Return -1 if the string
does not match the pattern (this is different from a zero-length
match!).
The optional second parameter, pos, gives an index in the string
where the search is to start; it defaults to 0. This is not
completely equivalent to slicing the string; the '' pattern
character matches at the real begin of the string and at positions
just after a newline, not necessarily at the index where the search
is to start.
- search (string[, pos])
-
Return the first position in string that matches the regular
expression pattern. Return -1 if no position in the
string matches the pattern (this is different from a zero-length
match anywhere!).
The optional second parameter has the same meaning as for the
match() method.
- group (index, index, ...)
-
This method is only valid when the last call to the match()
or search() method found a match. It returns one or more
groups of the match. If there is a single index argument,
the result is a single string; if there are multiple arguments, the
result is a tuple with one item per argument. If the index is
zero, the corresponding return value is the entire matching string; if
it is in the inclusive range [1..99], it is the string matching the
the corresponding parenthesized group (using the default syntax,
groups are parenthesized using \( and \)). If no
such group exists, the corresponding result is None.
If the regular expression was compiled by symcomp() instead of
compile(), the index arguments may also be strings
identifying groups by their group name.
Compiled regular expressions support these data attributes:
- regs
-
When the last call to the match() or search() method found a
match, this is a tuple of pairs of indexes corresponding to the
beginning and end of all parenthesized groups in the pattern. Indices
are relative to the string argument passed to match() or
search(). The 0-th tuple gives the beginning and end or the
whole pattern. When the last match or search failed, this is
None.
- last
-
When the last call to the match() or search() method found a
match, this is the string argument passed to that method. When the
last match or search failed, this is None.
- translate
-
This is the value of the translate argument to
regex.compile() that created this regular expression object. If
the translate argument was omitted in the regex.compile()
call, this is None.
- givenpat
-
The regular expression pattern as passed to compile() or
symcomp().
- realpat
-
The regular expression after stripping the group names for regular
expressions compiled with symcomp(). Same as givenpat
otherwise.
- groupindex
-
A dictionary giving the mapping from symbolic group names to numerical
group indexes for regular expressions compiled with symcomp().
None otherwise.
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