On 01May2022 18:55, Marco Sulla <marco.sulla.pyt...@gmail.com> wrote:
>Something like this is OK?
[...]
>def tail(f):
> chunk_size = 100
> size = os.stat(f.fileno()).st_size
I think you want os.fstat().
> positions = iter(range(size, -1, -chunk_size))
> next(positions)
I was wondering about the iter, but this makes sense. Alternatively you
could put a range check in the for-loop.
> chunk_line_pos = -1
> pos = 0
>
> for pos in positions:
> f.seek(pos)
> chars = f.read(chunk_size)
> chunk_line_pos = chars.rfind(b"\n")
>
> if chunk_line_pos != -1:
> break
Normal text file _end_ in a newline. I'd expect this to stop immediately
at the end of the file.
> if chunk_line_pos == -1:
> nbytes = pos
> pos = 0
> f.seek(pos)
> chars = f.read(nbytes)
> chunk_line_pos = chars.rfind(b"\n")
I presume this is because unless you're very lucky, 0 will not be a
position in the range(). I'd be inclined to avoid duplicating this code
and special case and instead maybe make the range unbounded and do
something like this:
if pos < 0:
pos = 0
... seek/read/etc ...
if pos == 0:
break
around the for-loop body.
> if chunk_line_pos == -1:
> line_pos = pos
> else:
> line_pos = pos + chunk_line_pos + 1
> f.seek(line_pos)
> return f.readline()
>
>This is simply for one line and for utf8.
And anything else where a newline is just an ASCII newline byte (10) and
can't be mistaken otherwise. So also ASCII and all the ISO8859-x single
byte encodings. But as Chris has mentioned, not for other encodings.
Seems sane. I haven't tried to run it.
Cheers,
Cameron Simpson <c...@cskk.id.au>
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