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