"for line in fd" twice

Peter Hansen peter at engcorp.com
Tue Jun 3 17:50:16 CEST 2003

"cqx": please don't top-post!

"cqx.purple.gold" wrote:

> Thomas Güttler <guettler at thomas-guettler.de> writes:
> > the following does not work:
> >
> > """
> > fd=open(file)
> > for line in fd:
> >     if line.startswith("mymark"):
> >         break
>   # seek backwards the length(line)
> > for line in fd:
> >     #Read lines after "mymark"
> >     ....
> > fd.close()
> > """
> You probably need to rewind the file using 'seek'.

I don't think he wants to go back to the beginning, although it
was a little unclear.  I think he wants to be able to continue
from where he left off...

Since with .readlines() the fd object maintains its state,
presumably if there is a similar approach using the implicit
iterator that is produced when you do "for line in fd" you
would be able to use that.  

I doubt you can do it with the implicit iterator, however, since
the reference to it would be lost after you exit the for block,
so why not try an *explicit* iterator:

fiter = iter(open(file))
for line in fiter:
   if line. blah blah: break

for line in fiter:
   if line  blah blah: break

This seems to work.


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