How to active the tab if the file is already opened?

I use the code to open my snippet. But if it already been opened, I just want to active the tab instead of open a new tab.
How to do that?

tabnew $VIM\vimfiles\bundle\vim-snipmate\snippets\python.snippets<CR>

--
--
You received this message from the "vim_use" maillist.
Do not top-post! Type your reply below the text you are replying to.
For more information, visit http://www.vim.org/maillist.php

---
You received this message because you are subscribed to the Google Groups "vim_use" group.
To unsubscribe from this group and stop receiving emails from it, send an email to vim_use+unsubscribe@googlegroups.com.
For more options, visit https://groups.google.com/d/optout.