Reading by positions plain text files

[Tim Harig]

On 2010-11-30, javivd <javiervandam at gmail.com> wrote:
> I have a case now in wich another file has been provided (besides the
> database) that tells me in wich column of the file is every variable,
> because there isn't any blank or tab character that separates the
> variables, they are stick together. This second file specify the
> variable name and his position:
>
> VARIABLE NAME	POSITION (COLUMN) IN FILE
> var_name_1 		123-123
> var_name_2 		124-125
> var_name_3 		126-126
> ..
> ..
> var_name_N 		512-513 (last positions)

I am unclear on the format of these positions.  They do not look like
what I would expect from absolute references in the data.  For instance,
123-123 may only contain one byte??? which could change for different
encodings and how you mark line endings.  Frankly, the use of the
world columns in the header suggests that the data *is* separated by
line endings rather then absolute position and the position refers to
the line number. In which case, you can use splitlines() to break up
the data and then address the proper line by index.  Nevertheless,
you can use file.seek() to move to an absolute offset in the file,
if that really is what you are looking for.