Indentation should be set to four spaces rather than a tab character. This is the recommendation given in the Python style guide found at Emacs should automatically set the tabstop correctly. For vi add the following lines to the vimrc file:

set tabstop=4
set shiftwidth=4
set expandtab

For UNIX systems, including Linux and Mac OS X, the vimrc file is /.vimrc whereas in MS Windows the file is $VIM/_vimrc which is usually C: \Program Files \vim \_vimrc. Certain versions of vim, those within the 6.2 series, contain a bug where the tabstop value cannot be changed using the vimrc file (although typing ``:set tabstop=4'' in vim will fix it). One solution is to edit the file python.vim which on GNU/Linux systems is located in the path /usr/share/vim/ftplugin/. It contains the two lines

" Python always uses a `tabstop' of 8.
setlocal ts=8

If these lines are deleted the bug will be removed. Another way to fix the problem is to install newer versions of the run-time files (which will do the same thing).

The relax user manual (PDF), created 2016-10-28.