正则表达式里的match()、search()函数与match()和search()函数的具体有什么区别呢?

#! /usr/bin/env python
# -*- coding=utf-8 -*-
import re
text = 'pythontab'
m = re.match(r"\w+", text)
if m:
  print m.group(0)
else:
  print 'not match'

#! /usr/bin/env python
# -*- coding=utf-8 -*-
#
import re
text = '@pythontab'
m = re.match(r"\w+", text)
if m:
  print m.group(0)
else:
  print 'not match'

#! /usr/bin/env python
# -*- coding=utf-8 -*-
#
import re
text = 'pythontab'
m = re.search(r"\w+", text)
if m:
  print m.group(0)
else:
  print 'not match'

#! /usr/bin/env python
# -*- coding=utf-8 -*-
#
import re
text = '@pythontab'
m = re.search(r"\w+", text)
if m:
  print m.group(0)
else:
  print 'not match'