Built-in open() with buffering > 1

[Hans Mulder]

On 24/08/12 06:35:27, Marco wrote:
> Please, can anyone explain me the meaning of the
> "buffering > 1" in the built-in open()?
> The doc says: "...and an integer > 1 to indicate the size
> of a fixed-size chunk buffer."
> So I thought this size was the number of bytes or chars, but
> it is not

The algorithm is explained at
http://docs.python.org/library/io.html#io.DEFAULT_BUFFER_SIZE

>> io.DEFAULT_BUFFER_SIZE
>>
>> An int containing the default buffer size used by the
>> module’s buffered I/O classes. open() uses the file’s
>> blksize (as obtained by os.stat()) if possible.

In other words: open() tries to find a suitable size by
calling os.stat(your_file).st_blksize and if that fails,
it uses io.DEFAULT_BUFFER_SIZE, which is 8192 on my box.

Whether you call open with buffering=2 or any larger
number, does not matter: the buffer size will be the
outcome of this algorithm.


Hope this helps,

-- HansM