I'm using a python library. I don't know about the indentation that the writer of that file used.
With gvim i press
Very likely, your source file contains both
spaces are the preferred indentation method. (From PEP8)
You can convert all
spaces by using those command:
:set expandtab :ret!
I suggest put those commands bellow in your
set expandtab softtabstop=4 tabstop=4 shiftwidth=4