List Manipulation

[Mike Kent]

Roman wrote:
> Thanks for your help
>
> My intention is to create matrix based on parsed csv file.  So, I would
> like to have a list of columns (which are also lists).
>
> I have made the following changes and it still doesn't work.
>
>
> cnt = 0
> p=[[], [], [], [], [], [], [], [], [], [], []]
> reader = csv.reader(file("f:\webserver\inp.txt"), dialect="excel",
>                          quotechar="'", delimiter='\t')
> for line in reader:
>     if cnt > 6:
>        break
>     j = 0
>     for col in line:
>        p[j].append(col)
>        j=j+1
>     cnt = cnt + 1
>
> print p

p[j] does not give you a reference to an element inside p.  It gives
you a new sublist containing one element from p.  You then append a
column to that sublist.  Then, since you do nothing more with that
sublist, YOU THROW IT AWAY.

Try doing:

p[j] = p[j].append(col)

However, this will still result in inefficient code.  Since every line
you read in via the csv reader is already a list, try this (untested)
instead:

reader = csv.reader(file("f:\webserver\inp.txt"), dialect="excel",
                         quotechar="'", delimiter='\t')
p = [ line for line in reader[:7] ]