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Re: Writing a stream of bytes

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  Re: Writing a stream of bytes Tim Chase <python.list@tim.thechases.com> - 2016-01-15 10:05 -0600

#101760 — Re: Writing a stream of bytes

On 2016-01-15 16:55, jmp wrote:
> 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
> 
> -- 
> https://mail.python.org/mailman/listinfo/python-list

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