Newby Question for reading a file

[Curt Hash]

On Thu, Feb 19, 2009 at 12:07 PM, steven.oldner <steven.oldner at gmail.com> wrote:
>
> On Feb 19, 12:40 pm, Mike Driscoll <kyoso... at gmail.com> wrote:
> > On Feb 19, 12:32 pm, "steven.oldner" <steven.old... at gmail.com> wrote:
> >
> > > Simple question but I haven't found an answer.  I program in ABAP, and
> > > in ABAP you define the data structure of the file and move the file
> > > line into the structure, and then do something to the fields.  That's
> > > my mental reference.
> >
> > > How do I separate or address each field in the file line with PYTHON?
> > > What's the correct way of thinking?
> >
> > > Thanks!
> >
> > I don't really follow what you mean since I've never used ABAP, but
> > here's how I typically read a file in Python:
> >
> > f = open("someFile.txt")
> > for line in f:
> >     # do something with the line
> >     print line
> > f.close()
> >
> > Of course, you can read just portions of the file too, using something
> > like this:
> >
> > f.read(64)
> >
> > Which will read 64 bytes. For more info, check the following out:
> >
> > http://www.diveintopython.org/file_handling/file_objects.html
> >
> >  - Mike
>
> Hi Mike,
>
> ABAP is loosely based on COBOL.
>
> Here is what I was trying to do, but ended up just coding in ABAP.
>
> Read a 4 column text file of about 1,000 lines and compare the 2
> middle field of each line.  If there is a difference, output the line.
>
> The line's definition in ABAP is PERNR(8) type c, ENDDA(10) type c,
> BEGDA(10) type c, and LGART(4) type c.
> In ABAP the code is:
> LOOP AT in_file.
>  IF in_file-endda <> in_file-begda.
>    WRITE:\ in_file. " that's same as python's print
>  ENDIF.
> ENDLOOP.
>
> I can read the file, but didn't know how to look st the fields in the
> line.  From what you wrote, I need to read each segment/field of the
> line?
>
> Thanks,
>
> Steve
> --
> http://mail.python.org/mailman/listinfo/python-list

You could do something like this:

f = open('file.txt', 'r')
for line in f:
    a,b = line.split()[1:-1]   # tokenize the string into sequence of
length 4 and store two middle values in a and b
    if a != b:
        print line
f.close()