regex - What is the difference between Python's re.search and re.match? -

what difference between search() , match() functions in python re module?

i've read documentation (current documentation), never seem remember it. keep having , re-learn it. i'm hoping answer examples (perhaps) stick in head. or @ least i'll have better place return question , take less time re-learn it.

re.match anchored @ beginning of string. has nothing newlines, not same using ^ in pattern.

as re.match documentation says:

if 0 or more characters @ beginning of string match regular expression pattern, return corresponding matchobject instance. return none if string not match pattern; note different zero-length match.

note: if want locate match anywhere in string, use search() instead.

re.search searches entire string, the documentation says:

scan through string looking location regular expression pattern produces match, , return corresponding matchobject instance. return none if no position in string matches pattern; note different finding zero-length match @ point in string.

so if need match @ beginning of string, or match entire string use match. faster. otherwise use search.

the documentation has specific section match vs. search covers multiline strings:

python offers 2 different primitive operations based on regular expressions: match checks match only @ beginning of string, while search checks match anywhere in string (this perl default).

note match may differ search when using regular expression beginning '^': '^' matches @ start of string, or in multiline mode following newline. “match” operation succeeds only if pattern matches @ start of string regardless of mode, or @ starting position given optional pos argument regardless of whether newline precedes it.

now, enough talk. time see 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) # won't match print re.search('someother',                  string_with_newlines) # finds print re.search('^someother', string_with_newlines,                  re.multiline) # finds  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) # matches