How do I create a variable where one index depends on the value of another index?

[Peter Otten]

giannis.dafnomilis at gmail.com wrote:

> Hey Peter.
> 
> This worked like a charm! I can't believe I did not think of that, after
> wasting so many hours on it.
> 
> Thank you so much for the help!

You can make these things easier to debug by breaking your code into small 
functions. If there were separate functions

def make_finalcosts(...):
   ...  # i is a local variable here

def make_probvars(...):
   ...  # i is not defined here and there's no global i

you'd have seen a NameError exception similar to the one below:

>>> def example(m, n):
...     return [i + k for j in range(m) for k in range(n)]
... 
>>> example(1, 2)
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "<stdin>", line 2, in example
  File "<stdin>", line 2, in <listcomp>
NameError: name 'i' is not defined

Writing a function in such a way that the result only depends on the 
function's arguments allows for easy testing.