Question

like this

text = "  \t  hello there\n  \t  how are you?\n  \t HHHH"
      hello there
      how are you?
     HHHH

Could I get the common prefix substring through regex?

I try to

In [36]: re.findall(r"(?m)(?:(^[ \t]+).+[\n\r]+\1)", "  \t  hello there\n  \t  how are you?\n  \t HHHH")
Out[36]: ['  \t  ']

But apparently that common prefix substring is ‘ \t ‘
I want use for dedent function like python textwrap module.

Answer 1

I suggest

match = re.search(r'(?m)\A(.*).*(?:\n?^\1.*$)*\n?\Z', text)

See this demo.