for line in ftpr: and fptr.tell()

[Jamey Cribbs]

Is it still true that you can't do:

for line in fptr:
pos = fptr.tell()


Because you won't get the correct file position from tell(). I think it
had something to do with the file iterator caching several kb of the
file when it first started the for loop.

Is there a fix/work-around for this?

Thanks!

Jamey Cribbs

 

[Erik Max Francis]

Because you won't get the correct file position from tell(). I think
it
had something to do with the file iterator caching several kb of the
file when it first started the for loop.

Is there a fix/work-around for this?

Yes. Use:

while True:
line in F.readline()
if not line:
break
pos = F.tell()
...

Seriously, the problem here is that iterating over a while has the same
effect as F.xreadlines() For efficiency, the reads are buffered, so
interacting with the file object while you're using one of these methods
results in weird behavior. If you want to interact with the file object
while you're also reading in lines, you should not use either of those
mechanisms.