Path: csiph.com!fu-berlin.de!uni-berlin.de!not-for-mail From: jmp Newsgroups: comp.lang.python Subject: Writing a stream of bytes Date: Fri, 15 Jan 2016 16:55:08 +0100 Lines: 38 Message-ID: Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit X-Trace: news.uni-berlin.de XCyAn6jOnYk4AOOhGFrcSgrbyxKcPwKAJ8VFyTlGC60w== Return-Path: X-Original-To: python-list@python.org Delivered-To: python-list@mail.python.org X-Spam-Status: OK 0.004 X-Spam-Evidence: '*H*': 0.99; '*S*': 0.00; 'bytes.': 0.07; '(instead': 0.09; 'endian': 0.09; 'received:80.91': 0.09; 'received:80.91.229': 0.09; 'received:gmane.org': 0.09; 'received:list': 0.09; 'subject:Writing': 0.09; 'received:80.91.229.3': 0.16; 'received:io': 0.16; 'received:plane.gmane.org': 0.16; 'received:psf.io': 0.16; 'bytes': 0.18; 'tells': 0.18; 'file:': 0.22; 'struct': 0.22; 'cheers,': 0.22; 'file.': 0.22; 'seems': 0.23; 'import': 0.24; 'module': 0.25; 'header:User-Agent:1': 0.26; 'header:X-Complaints- To:1': 0.26; 'actual': 0.28; "i'd": 0.31; 'maybe': 0.33; 'stream': 0.33; 'file': 0.34; 'but': 0.36; 'to:addr:python-list': 0.36; 'say': 0.37; 'received:org': 0.37; 'end': 0.39; 'rather': 0.39; 'to:addr:python.org': 0.40; 'received:194': 0.61; 'more': 0.63; 'note:': 0.66; 'order:': 0.84; 'overlooked': 0.84; 'struct.': 0.84 X-Injected-Via-Gmane: http://gmane.org/ X-Gmane-NNTP-Posting-Host: paris.sequans.com User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Thunderbird/31.6.0 X-BeenThere: python-list@python.org X-Mailman-Version: 2.1.20+ Precedence: list List-Id: General discussion list for the Python programming language List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Xref: csiph.com comp.lang.python:101758 Hi pyple ! I'd like to write a stream of bytes into a file. I'd like to use the struct (instead of bytearray) module because I will have to write more than bytes. let's say I want a file with 4 bytes in that order: 01 02 03 04 None of these work: import struct with open('toto', 'wb') as f: f.write(struct.pack('4B', *[1,2,3,4])) with open('toto', 'wb') as f: f.write(struct.pack('<4B', *[1,2,3,4])) with open('toto', 'wb') as f: f.write(struct.pack('>4B', *[1,2,3,4])) I always end up with the following bytes on file: !hexdump toto 0000000 0201 0403 Note: the '<' and '>' tells struct to pack for a litle/big endian architecture. The only solution I came up with is with open('toto', 'wb') as f: f.write(struct.pack('>4B', *[2,1,4,3])) But I'd rather not manipulate the stream, as it seems to me that this would be the job of struct. Or maybe I completely overlooked the actual issue ? Cheers, jm