Reading a file and resuming reading.

[Hrvoje Niksic]

"Karim Ali" <kakeez at hotmail.com> writes:

> -----------------------------
> while not eof  <- really want the EOF and not just an empty line!
>     readline by line
> end while;
> -----------------------------

for line in open_file:
  ...

It will stop on EOF, not on empty line.

> But also, in case for one reason or another the program crashes, I
> want to be able to rexecute it and for it to resume reading from the
> same position as it left. If a while loop like the one above can be
> implemented I can do this simply by counting the lines!

If you open the file in binary mode, you can easily keep track of the
position in file:

bytepos = 0
with file(filename) as f:
  for line in f:
    ... process line ...
    bytepos += len(line)

If you need to restart the operation, simply seek to the previously
known position:

# restart with old bytyepos
with file(filename) as f:
  f.seek(bytepos)
  for line in f:
    ... process line ...
    bytepos += len(line)