How to run Vim shell from script's path?

Search results returned tones of Q&As and I don't know how to rephrase this better, so pardon me if it's a duplicate:

I'm running a python script with Vim. The script is at ~/path/to/my/script.py and there is a style sheet file in the same path.

The code's content opens the file:

f = open('./stylesheet.css', 'r')
s = f.read()
f.close()

And if I r开发者_JS百科un my code from Vim like so :!python %,it will return: IOError: [Errno 2] No such file or directory: 'stylesheet.css'

So it seems Vim runs my code not from the code's location, but from /home or root?

How can I make it use the code's path as the root path during execution?

You can use this :lcd %:p:h | !python %.

A brief explanation. lcd changes directory to the current file being edited - http://vim.wikia.com/wiki/Set_working_directory_to_the_current_file

Then executes the python command on the file.

The one problem with this command is that your current directory will now be (from your example) ~/path/to/my/. You will have to do another :lcd to get back to your current directory. I wasn't able to find a way to combine all of it into one command in vim. Maybe someone else can.

Edit - How-to cd back again

(removed my complex method)

for the simple solution refer to ib's comments below.

To open a file in the same directory as your script, try something like:

import os

script_dir = os.path.dirname(__file__)
target_file = os.path.join(script_dir, 'stylesheet.css')

with open(target_file, 'r') as f:
  s = f.read()

The shortcut in vim for the current file is %, so instead of :!python $, type :!python %