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authorFred Drake <fdrake@acm.org>1998-12-22 18:19:45 (GMT)
committerFred Drake <fdrake@acm.org>1998-12-22 18:19:45 (GMT)
commit768ac6b804dc41f72e55b04a26f888e8f600fbae (patch)
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parent5eecd7b3bd5e78210f05e5a8757d78430d855bc0 (diff)
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Start of text that describes differences between match and search.
Strengthen pointers to the search() function and method.
Diffstat (limited to 'Doc/lib/libre.tex')
-rw-r--r--Doc/lib/libre.tex45
1 files changed, 40 insertions, 5 deletions
diff --git a/Doc/lib/libre.tex b/Doc/lib/libre.tex
index 6318350..81bfd92 100644
--- a/Doc/lib/libre.tex
+++ b/Doc/lib/libre.tex
@@ -282,6 +282,35 @@ for the current locale.
\end{list}
+\subsection{Matching vs. Searching \label{matching-searching}}
+\sectionauthor{Fred L. Drake, Jr.}{fdrake@acm.org}
+
+\strong{XXX This section is still incomplete!}
+
+Python offers two different primitive operations based on regular
+expressions: match and search. If you are accustomed to Perl's
+semantics, the search operation is what you're looking for. See the
+\function{search()} function and corresponding method of compiled
+regular expression objects.
+
+Note that match may differ from search using a regular expression
+beginning with \character{\^}: \character{\^} matches only at the start
+of the string, or in \constant{MULTILINE} mode also immediately
+following a newline. "match" succeeds only if the pattern matches at
+the start of the string regardless of mode, or at the starting
+position given by the optional \var{pos} argument regardless of
+whether a newline precedes it.
+
+% Examples from Tim Peters:
+\begin{verbatim}
+re.compile("a").match("ba", 1) # succeeds
+re.compile("^a").search("ba", 1) # fails; 'a' not at start
+re.compile("^a").search("\na", 1) # fails; 'a' not at start
+re.compile("^a", re.M).search("\na", 1) # succeeds
+re.compile("^a", re.M).search("ba", 1) # fails; no preceding \n
+\end{verbatim}
+
+
\subsection{Module Contents}
\nodename{Contents of Module re}
@@ -376,6 +405,9 @@ leftmost such \character{\#} through the end of the line are ignored.
\class{MatchObject} instance. Return \code{None} if the string does not
match the pattern; note that this is different from a zero-length
match.
+
+ \strong{Note:} If you want to locate a match anywhere in
+ \var{string}, use \method{search()} instead.
\end{funcdesc}
\begin{funcdesc}{split}{pattern, string, \optional{, maxsplit\code{ = 0}}}
@@ -387,7 +419,7 @@ leftmost such \character{\#} through the end of the line are ignored.
element of the list. (Incompatibility note: in the original Python
1.5 release, \var{maxsplit} was ignored. This has been fixed in
later releases.)
-%
+
\begin{verbatim}
>>> re.split('\W+', 'Words, words, words.')
['Words', 'words', 'words', '']
@@ -396,7 +428,7 @@ leftmost such \character{\#} through the end of the line are ignored.
>>> re.split('\W+', 'Words, words, words.', 1)
['Words', 'words, words.']
\end{verbatim}
-%
+
This function combines and extends the functionality of
the old \function{regsub.split()} and \function{regsub.splitx()}.
\end{funcdesc}
@@ -417,7 +449,7 @@ unchanged. \var{repl} can be a string or a function; if a function,
it is called for every non-overlapping occurance of \var{pattern}.
The function takes a single match object argument, and returns the
replacement string. For example:
-%
+
\begin{verbatim}
>>> def dashrepl(matchobj):
.... if matchobj.group(0) == '-': return ' '
@@ -425,7 +457,7 @@ replacement string. For example:
>>> re.sub('-{1,2}', dashrepl, 'pro----gram-files')
'pro--gram files'
\end{verbatim}
-%
+
The pattern may be a string or a
regex object; if you need to specify
regular expression flags, you must use a regex object, or use
@@ -498,7 +530,10 @@ attributes:
\class{MatchObject} instance. Return \code{None} if the string does not
match the pattern; note that this is different from a zero-length
match.
-
+
+ \strong{Note:} If you want to locate a match anywhere in
+ \var{string}, use \method{search()} instead.
+
The optional second parameter \var{pos} gives an index in the string
where the search is to start; it defaults to \code{0}. This is not
completely equivalent to slicing the string; the \code{'\^'} pattern