Re: Splitting a float into bytes:
Michael Yanowitz wrote: > Hello: > > For some reason I can't figure out how to split > a 4-byte (for instance) float number (such as 3.14159265359) > into its 4-bytes so I can send it via a socket to another > computer. > For integers, it is easy, I can get the 4 bytes by anding like: > byte1 = int_val & 0x00FF > byte2 = int_val & 0xFF00 > byte3 = int_val & 0x00FF > byte4 = int_val & 0xFF00 Errrmmm ... I think you need the right shift operator e.g. byte4 = (int_val & 0xFF00) >> 24 but assert 0 <= byte4 <= 255 may fail under some circumstances so (better): byte4 = (int_val >> 24) & 0xFF # absolutely guaranteed to pass that assertion BUT why muck around with all that when you can use struct.pack??? -- http://mail.python.org/mailman/listinfo/python-list
Re: Splitting a float into bytes:
Michael Yanowitz wrote: > -Original Message- > From: [EMAIL PROTECTED] > [mailto:[EMAIL PROTECTED] Behalf > Of Simon Forman > Sent: Wednesday, July 26, 2006 2:56 PM > To: python-list@python.org > Subject: Re: Splitting a float into bytes: > > > Michael Yanowitz wrote: > > Hello: > > > > For some reason I can't figure out how to split > > a 4-byte (for instance) float number (such as 3.14159265359) > > into its 4-bytes so I can send it via a socket to another > > computer. > > For integers, it is easy, I can get the 4 bytes by anding like: > > byte1 = int_val & 0x00FF > > byte2 = int_val & 0xFF00 > > byte3 = int_val & 0x00FF > > byte4 = int_val & 0xFF00 > > But if I try to do that with floats I get: > > >>> pi & 0xFF > > Traceback (most recent call last): > > File "", line 1, in ? > > TypeError: unsupported operand type(s) for &: 'float' and 'int' > > > > Is there some easy way to get what the bytes of the float are? > > > > Thanks in advance: > > Michael Yanowitz > > The struct module. (It also works for ints. ;-) ) > > http://docs.python.org/lib/module-struct.html > > > HTH, > ~Simon > >Thanks, but maybe I am missing something. > If I use pack, doesn't it have to be unpacked at the other end > to make sense? The data will be picked up on some other computer > by some other application probably written in C or C++. Would > it have to be rewritten to unpack the data? > > Thanks in advance: > Michael Yanowitz It says in the docs "This module performs conversions between Python values and C structs represented as Python strings." This means, to me, that the packed data will be in the format that C (and C++ I would assume) uses. You might have to mind the endian-ness if you're transferring data between different architectures, but struct includes format specifiers for this. Have fun, ~Simon -- http://mail.python.org/mailman/listinfo/python-list
Re: Splitting a float into bytes:
Yes i think you can. If you use the struct module.
>> import struct
>> import math
>>y = struct.pack('!f', math.pi)
>>print repr(y)
'@I\x0f\xdb'
"Michael Yanowitz" <[EMAIL PROTECTED]> wrote in message
news:[EMAIL PROTECTED]
> Hello:
>
> For some reason I can't figure out how to split
> a 4-byte (for instance) float number (such as 3.14159265359)
> into its 4-bytes so I can send it via a socket to another
> computer.
> For integers, it is easy, I can get the 4 bytes by anding like:
> byte1 = int_val & 0x00FF
> byte2 = int_val & 0xFF00
> byte3 = int_val & 0x00FF
> byte4 = int_val & 0xFF00
> But if I try to do that with floats I get:
pi & 0xFF
> Traceback (most recent call last):
> File "", line 1, in ?
> TypeError: unsupported operand type(s) for &: 'float' and 'int'
>
> Is there some easy way to get what the bytes of the float are?
>
> Thanks in advance:
> Michael Yanowitz
>
>
--
http://mail.python.org/mailman/listinfo/python-list
RE: Splitting a float into bytes:
-Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] Behalf Of Simon Forman Sent: Wednesday, July 26, 2006 2:56 PM To: python-list@python.org Subject: Re: Splitting a float into bytes: Michael Yanowitz wrote: > Hello: > > For some reason I can't figure out how to split > a 4-byte (for instance) float number (such as 3.14159265359) > into its 4-bytes so I can send it via a socket to another > computer. > For integers, it is easy, I can get the 4 bytes by anding like: > byte1 = int_val & 0x00FF > byte2 = int_val & 0xFF00 > byte3 = int_val & 0x00FF > byte4 = int_val & 0xFF00 > But if I try to do that with floats I get: > >>> pi & 0xFF > Traceback (most recent call last): > File "", line 1, in ? > TypeError: unsupported operand type(s) for &: 'float' and 'int' > > Is there some easy way to get what the bytes of the float are? > > Thanks in advance: > Michael Yanowitz The struct module. (It also works for ints. ;-) ) http://docs.python.org/lib/module-struct.html HTH, ~Simon Thanks, but maybe I am missing something. If I use pack, doesn't it have to be unpacked at the other end to make sense? The data will be picked up on some other computer by some other application probably written in C or C++. Would it have to be rewritten to unpack the data? Thanks in advance: Michael Yanowitz -- http://mail.python.org/mailman/listinfo/python-list
Re: Splitting a float into bytes:
Michael Yanowitz wrote: > Hello: > > For some reason I can't figure out how to split > a 4-byte (for instance) float number (such as 3.14159265359) > into its 4-bytes so I can send it via a socket to another > computer. > For integers, it is easy, I can get the 4 bytes by anding like: > byte1 = int_val & 0x00FF > byte2 = int_val & 0xFF00 > byte3 = int_val & 0x00FF > byte4 = int_val & 0xFF00 > But if I try to do that with floats I get: > >>> pi & 0xFF > Traceback (most recent call last): > File "", line 1, in ? > TypeError: unsupported operand type(s) for &: 'float' and 'int' > > Is there some easy way to get what the bytes of the float are? > > Thanks in advance: > Michael Yanowitz The struct module. (It also works for ints. ;-) ) http://docs.python.org/lib/module-struct.html HTH, ~Simon -- http://mail.python.org/mailman/listinfo/python-list
