question about [0] in os module

[PyGIS]

Hi friends:

i'm beginner in python . i have a question . what does [0] mean in the below code and when should i use [0] in codes ?

import os
import string

def replace(file, search_for, replace_with):
    # replace strings in a text file

    back = os.path.splitext(file)[B][0][/B] + ".bak"
    temp = os.path.splitext(file)[B][0][/B] + ".tmp"

    try:
        # remove old temp file, if any
        os.remove(temp)
    except os.error:
        pass

    fi = open(file)
    fo = open(temp, "w")

[Mc1brew]

Not knowing Python... My guess would be SplitText returns an array, and [0] indicates that it should return the first element (indexing from 0)...