manipulating .xls data

[caroundw5h]

I would like to manipulate my excel file as if it were a text file
with python (check for duplicates, uppercase etc.). I would like to
know:

1) how do convert it first to a CSV file and manipulate it.

2) are there any functiionalities in excel that will allow me to
create my own functions.

3) what is the best way to manipualte excel files OTHER than COM.


thank you all