Python正则表达式实现截取成对括号的方法

strs = '1(2(3(4(5(67)6)7)8)9)0'
reg1 = re.compile('([()])∗') #一对括号
reg2 = re.compile('([()]|\([()]∗)*\)') #两对括号
reg3 = re.compile('([()]|\([()]∗|([()]|\([()]∗)*\))*\)') #三层

#匹配成对括号正则表达式
def getReg(self, count, bracket = '()'):
    leftBracket = bracket[0]
    rightBracket = bracket[1]
    count -= 1
    regBasic = leftBracket + '(?:[^' + leftBracket + rightBracket + '])*' + rightBracket
    if count < 0:
      regBasic = &#39;&#39;
    if count > 0:
      for i in xrange(count):
        tempNum = regBasic.rfind(&#39;*&#39;) - 1
        regBasic = regBasic[:tempNum] + "|" + regBasic + regBasic[tempNum:]
    return regBasic