>>> str1
'this register include two status:\n 1: active;\n 0: in-active.'
>>> str4 = re.sub(r' {2,}', repl, str1)
>>> print(str4)
this register include two status:
nbsp;nbsp;1: active;
nbsp;nbsp;0: in-active.
注意：其中的repl是一个函数，定义如下：
>>> def repl(m):
... return 'nbsp;' * len(m.group())
