Text Manipulation in Python

[Edward Hasted]

I am completely new to Python.

We want to use it to alter specific lines in template files, typically 
something like changing:-

Variable = 1234

to 

Variable = Company Name

The text manipulation strings within Python seem to work sequentially 
rather than on a line basis.

1. Is this correct?
2. What is the best way to do text searching and manipulation within 
Python.

Many thanks,

Edward