[Python-Dev] new buffer in python2.7 (original) (raw)

Kristján Valur Jónsson kristjan at ccpgames.com
Wed Oct 27 14:00:10 CEST 2010

Ah, well in 2.7 you don't have the luxury of a bytes object. A str() would be similar in 2.7 Anyway, isn't the "bytes" object immutable? In that case, it is not a useful target for a sock.recv_into() call. Calling getbuffer on a bytearray or a bytes object should be really cheap, so I still don't accept this as a matter of fact situation.

Btw, going to 3.2 isn't a real option for us any time soon. A lot of companies probably find themselves in a similar situation. This is why I spend so much effort applying some love to 2.7. Most of the stuff I locally do to 2.7 I then contribute to python as 3.2 patches. Someday they'll get backported, no doubt :)

K

-----Original Message----- From: python-dev-bounces+kristjan=ccpgames.com at python.org [mailto:python-dev-bounces+kristjan=ccpgames.com at python.org] On Behalf Of Antoine Pitrou Sent: Wednesday, October 27, 2010 19:16 To: python-dev at python.org Subject: Re: [Python-Dev] new buffer in python2.7

>Here are micro-benchmarks under 3.2:

> $ ./python -m timeit -s "x = b'x'*10000" "x[:100]" > 10000000 loops, best of 3: 0.134 usec per loop $ ./python -m timeit > -s "x = memoryview(b'x'*10000)" "x[:100]" > 10000000 loops, best of 3: 0.151 usec per loop That's weird. The greedy slice needs two memory allocations. One for the ByteArray object itself, one for its cargo. In total, more that 100 bytes. In contrast, creating the MemoryView object requires only one allocation of a few dozen bytes.

It's not a bytearray object, it's a bytes object. It requires only a single allocation since the data is allocated inline. The memoryview object must also call getbuffer() again on the original object.

Regards

Antoine.

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