re.match
is anchored at the beginning of the string. That has nothing to do with newlines, so it is not the same as using ^
in the pattern.
As re.match documentation says:
If zero or more characters at the
beginning of string match the regular expression pattern, return a
corresponding MatchObject
instance.
Return None
if the string does not
match the pattern; note that this is
different from a zero-length match.
Note: If you want to locate a match
anywhere in string, use search()
instead.
re.search
searches the entire string, as the documentation says:
Scan through string looking for a
location where the regular expression
pattern produces a match, and return a
corresponding MatchObject
instance.
Return 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.
So if you need to match at the beginning of the string, or to match the entire string use match
. It is faster. Otherwise use search
.
The documentation has a specific section for match
vs. search
that also covers multiline strings:
Python offers two different primitive
operations based on regular
expressions: match
checks for a match
only at the beginning of the string,
while search
checks for a match
anywhere in the string (this is what
Perl does by default).
Note that match
may differ from search
even when using a regular expression
beginning with '^'
: '^'
matches only
at the start of the string, or in
MULTILINE
mode also immediately
following a newline. The “match
”
operation succeeds only if the pattern
matches at the start of the string
regardless of mode, or at the starting
position given by the optional pos
argument regardless of whether a
newline precedes it.
Now, enough talk. Time to some example code:
# example code:
string_with_newlines = """something
someotherthing"""
import re
print re.match('some', string_with_newlines) # matches
print re.match('someother',
string_with_newlines) # won't match
print re.match('^someother', string_with_newlines,
re.MULTILINE) # also won't match
print re.search('someother',
string_with_newlines) # finds something
print re.search('^someother', string_with_newlines,
re.MULTILINE) # also finds something
m = re.compile('thing$', re.MULTILINE)
print m.match(string_with_newlines) # no match
print m.match(string_with_newlines, pos=4) # matches
print m.search(string_with_newlines,
re.MULTILINE) # also matches