python - Regular Expressions: Special Characters and Tab Spaces -

i testing out function wrote. supposed give me count of full stops (.) in line or string. full stop (.) interested in counting has tab space before , after it.

here have written.

def seek():    = '1   .   .   3   .'    b = a.count(r'\t\.\t')    return b seek() 

however, when test it, returns 0. a, there 2 full stops (.) both tab space before , after it. using regular expressions improperly? represented incorrectly? appreciated.

thanks.

it doesn't a has tabs in it. although may have hit tab key on keyboard, character have been interpreted text editor "insert number of spaces align next tab character". need line this:

a = '1\t.\t.\t3\t.' 

that should it.

a more complete example:

from re import * def seek():    = '1\t.\t.\t3\t\.'    re = compile(r'(?<=\t)\.(?=\t)');    return len(re.findall(a)) print seek() 

this uses "lookahead" , "lookbehind" match tab character without consuming it. mean? means when have \t.\t.\t, match both first , second \.. original expression have matched initial \t\.\t and discarded them. after, there have been \. nothing in front of it, , no second match. lookaround syntax "zero width" - expression tested ends taking no space in final match. thus, code snippet gave returns 2, expect.