Edit Python code programmatically

[Alex]

Which library could you recommend to perform simple editing of Python 
code (from Python program)? For example, open *.py file, find specific 
function definition, add another function call inside, find existing 
call and change parameter value, etc.

What I'm trying to implement isn't a real visual programming tool, but 
some code-generation is necessary. For now I think I can generate Python 
syntax manually (like any text file), but it can become more complicated 
in future (like partially implementing code-generation library), plus 
there'll always be possibility of corrupting files and losing data (or 
having to recover valid Python syntax manually) due to coding mistake.

Thanks