I need some help with a little of python scripting. I'm trying to make my script to do this following.

Xterminal:

root
echo 78> /abc/abc/bca


i've tried this but nothing work.

If I run this from Xterminal as root:
root
python
import os
os.system('echo 78> /abc/abc/bca')

it works!

But if I run from script it doesnt. How can i get it to work?

The file is not changing.
How do I achieve this same effect with python?