Lorn wrote:
> I'm trying to figure out a way to create dynamic lists or possibly
> antother solution for the following problem. I have multiple lines in a
> text file (every line is the same format) that are iterated over and
> which need to be compared to previous lines in the file in order to
> perform some simple math. Each line contains 3 fileds: a descriptor and
> two integers. Here is an example:
>
> rose, 1, 500
> lilac, 1, 300
> lilly, 1, 400
> rose, 0, 100
Do you have to maintain a list or just the current value?
Also I did not find it clear why you have to compare with previous line?
Anyway, I think dictionnary may be useful there:
>>> input = """rose, 1, 500
... lilac, 1, 300
... lilly, 1, 400
... rose, 0, 100"""
>>>
>>> entries = [l.split(',') for l in input.split('\n')]
>>>
>>> d = {}
>>> for k, op, n in entries:
... if int(op) == 1:
... d[k] = d.get(k, 0) + int(n)
... else:
... d[k] = d.get(k, 0) - int(n)
...
>>> print d
{'rose': 400, 'lilly': 400, 'lilac': 300}
>>>
That may not be what you want but there may be some things for you to use.
And you can of course keep the full list of operation in d.
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