automatic indenting python when using vim editor

Create a directory under ~/.vim, called ftplugin. Then create a file called python.vim there:

 $mkdir ~/.vim/ftplugin  

 $vim ~/.vim/ftplugin/python.vim  

Insert the following into python.vim
setlocal tabstop=4
setlocal softtabstop=4
setlocal shiftwidth=4
setlocal textwidth=80
setlocal smarttab
setlocal expandtab

create a file named as .vimrc under ~

 $vim ~/.vimrc  

There insert the following text
filetype plugin indent on

Now if you write a .py script in vim, hitting tab once will indent by 4 blankspaces.