[Tutor] manipulating data

[Bryan Fodness]

I have tried,

f = open('TEST1.MLC')
fields = {}
for line in f:
  the_line = line.split()
  if the_line:
    if the_line[0] == 'Field':
      field = int(the_line[-1])
    elif the_line[0] == 'Leaf':
      fields[field] = the_line[-1]

which, sort of works, but it overwrites each value.

On Nov 12, 2007 6:55 PM, Alan Gauld <alan.gauld at btinternet.com> wrote:
> The lesson here is not to try to do two things at once...
>
> >         file.next()
> >     TypeError: descriptor 'next' of 'file' object needs an argument
>
> OK, My algorithm was meant to be pseudo code so file was
> not intended to be taken literally, its just a marker for an open
> file object.
>
> > And, it is true that I am trying to build a list and not overwrite
> > the value.
>
> OK, That adds a bit more tweaking...
>
> >> Personally I'd use a flag to detect when field had
> >> been found and set - ie set field to None and then
> >> test for that changing, then test for Leaf as you do.
>
> That was before I went back to testing my own project....
>
> >> So I think your algorithm should be
> >>
> >> for line in file
> >>    if 'Field' in line:
> >>       field = int(line.split()[-1])
>
> and this was after - with no flag anywhere in sight! Oops.
>
> I intended the if test to include a check for field == None...
>
> if field == None and 'Field' in line:....
>
> >>    elif 'Leaf' in line:
> >>       fields[field] = line.split()[-1]
> >>    else: file.next()
> >>
> >> But I think there's another problem in that you are
> >> then overwriting the value of Leaf when I think you
> >> are trying to build a list?
>
> So we need to create an empty list entry where we
> define field and then append here, so my pseudo
> code now becomes:
>
> f = open('foo.dat')
> for line in f:
>    if field == None and 'Field' in line:
>       field = int(line.split()[-1])
>       fields[field] = []
>    elif 'Leaf' in line:
>       fields[field].append(line.split()[-1])
>    else: f.next()
>
> still untested I'm afraid, so it still may not work.
>
> HTH,
>
> Alan G.
>
>
>
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