Strange (for a newbie) problem

[Angelo Secchi]

I'm experiencing the following problem. 
I have a python script analyses.py where a certain point I have to
define a variable called 'code' like:

code=151

The program works fine but if I change that line in 'code=sys.argv[1]'
using the sys module in order to give to the program that code as a
parameter (i.e. I then run this script as "python analyses.py 151" from
the shell) then the program returns an error complaining that a certain
variable different from code is not defined.

What is my mistake?
Thanks
angelo