解决python正则表达式出现：sre_constants.error: multiple repeat at position 3

一，问题出现：

这是在Python　IDLE 中运行出现的情况:

>>> pattern = '(.?*)(\d+)'
>>> s = '第1章 绪论  1'
>>> re.findall(pattern, s)
Traceback (most recent call last):
  File "/usr/lib/python3.6/code.py", line 91, in runcode
    exec(code, self.locals)
  File "", line 1, in 
  File "/usr/lib/python3.6/re.py", line 222, in findall
    return _compile(pattern, flags).findall(string)
  File "/usr/lib/python3.6/re.py", line 301, in _compile
    p = sre_compile.compile(pattern, flags)
  File "/usr/lib/python3.6/sre_compile.py", line 562, in compile
    p = sre_parse.parse(p, flags)
  File "/usr/lib/python3.6/sre_parse.py", line 855, in parse
    p = _parse_sub(source, pattern, flags & SRE_FLAG_VERBOSE, 0)
  File "/usr/lib/python3.6/sre_parse.py", line 416, in _parse_sub
    not nested and not items))
  File "/usr/lib/python3.6/sre_parse.py", line 765, in _parse
    p = _parse_sub(source, state, sub_verbose, nested + 1)
  File "/usr/lib/python3.6/sre_parse.py", line 416, in _parse_sub
    not nested and not items))
  File "/usr/lib/python3.6/sre_parse.py", line 619, in _parse
    source.tell() - here + len(this))
sre_constants.error: multiple repeat at position 3

>>> pattern = '.?*(\d+)'
>>> re.findall(pattern, s)
Traceback (most recent call last):
  File "/usr/lib/python3.6/code.py", line 91, in runcode
    exec(code, self.locals)
  File "", line 1, in 
  File "/usr/lib/python3.6/re.py", line 222, in findall
    return _compile(pattern, flags).findall(string)
  File "/usr/lib/python3.6/re.py", line 301, in _compile
    p = sre_compile.compile(pattern, flags)
  File "/usr/lib/python3.6/sre_compile.py", line 562, in compile
    p = sre_parse.parse(p, flags)
  File "/usr/lib/python3.6/sre_parse.py", line 855, in parse
    p = _parse_sub(source, pattern, flags & SRE_FLAG_VERBOSE, 0)
  File "/usr/lib/python3.6/sre_parse.py", line 416, in _parse_sub
    not nested and not items))
  File "/usr/lib/python3.6/sre_parse.py", line 619, in _parse
    source.tell() - here + len(this))
sre_constants.error: multiple repeat at position 2

问题出在正则的写法存在问题，因此去掉?或者*均可，具体看你要匹配的对象。

二，解决问题

>>> pattern = '(.*)(\d+)'
>>> re.findall(pattern, s)
[('第1章 绪论  ', '1')]
>>> regex = re.compile(r'(.*)(\d+)')
>>> result = regex.search(s)
>>> result.group()
'第1章 绪论  1'
>>> result.group(1)
'第1章 绪论  '
>>> result.group(2)
'1'

.*是贪婪匹配，.*?是非贪婪匹配。