[EMAIL PROTECTED] wrote:
> Hello,
>
> I am having trouble writing the code to read a binary string. I would
> like to extract the values for use in a calculation.
>
> Any help would be great.
>
Without having looked at your code an any detail, may I humbly suggest
that you throw it all out and use the struct module:
http://docs.python.org/lib/module-struct.html
It is meant to solve this kind of problem, and it is quite easy to use.
Gary Herron
> Here is my function that takes in a string.
>
> def parseSequence(data, start):
>
> group_num = data[start:start+2]
> element_num = data[start+2:start+4]
> vl_field = data[start+4:start+8]
> length = struct.unpack('hh', vl_field)[0]
> value = data[start+8:(start+8+length)]
> pos = start+8+length
> element = (group_num+element_num)
>
> if element == '\xfe\xff\x00\xe0':
> data = value
>
> while start < length:
> group_num = data[start:start+2]
> element_num = data[start+2:start+4]
> vl_field = data[start+4:start+8]
> length = struct.unpack('hh', vl_field)[0]
> value = data[start+8:(start+8+length)]
> start = start+8+length
> element = (group_num+element_num)
>
> if element == '\xfe\xff\x00\xe0':
> data = value
>
> while start < length:
> group_num = data[start:start+2]
> element_num = data[start+2:start+4]
> vl_field = data[start+4:start+8]
> length = struct.unpack('hh', vl_field)[0]
> value = data[start+8:(start+8+length)]
> start = start+8+length
> element = (group_num+element_num)
> return element, start, value
>
> else:
> return element, start, value
>
> else:
> return element, pos, value
>
> And, here is a sample string (I have split up and indented for
> readability). There is an identifier (\xfe\xff\x00\xe0) followed by
> the length of the nested values.
>
>
> '\xfe\xff\x00\xe0\x18\x02\x00\x00 -length=536
> \n0q\x00\x02\x00\x00\x001
> \n0x\x00\x02\x00\x00\x0010
> \n0\x80\x00\x02\x00\x00\x004
> \n0\xa0\x00\x02\x00\x00\x000
> \x0c0\x04\x00\xe8\x01\x00\x00
> \xfe\xff\x00\xe0p\x00\x00\x00 -length=112
> \n0\x82\x002\x00\x00\x0042.9068704277562\\-392.3545926477\
> \189.182112099444
> \n0\x84\x00\x0c\x00\x00\x008.9617062e-1
> \n0\x86\x00\x10\x00\x00\x00127.378510918301
> \x0c0\x06\x00\x02\x00\x00\x001
> \xfe\xff\x00\xe0p\x00\x00\x00 -length=112
> \n0\x82\x002\x00\x00\x0042.9068704277562\\-392.3545926477\
> \189.182112099444
> \n0\x84\x00\x0c\x00\x00\x001.629998e-1
> \n0\x86\x00\x10\x00\x00\x0023.159729257873
> \x0c0\x06\x00\x02\x00\x00\x004
> \xfe\xff\x00\xe0t\x00\x00\x00 -length=116
> \n0\x82\x002\x00\x00\x0042.9068704277562\\-392.3545926477\
> \189.182112099444
> \n0\x84\x00\x10\x00\x00\x001.26285318894435
> \n0\x86\x00\x10\x00\x00\x00227.690980638769
> \x0c0\x06\x00\x02\x00\x00\x003
> \xfe\xff\x00\xe0t\x00\x00\x00 -length=116
> \n0\x82\x002\x00\x00\x0042.9068704277562\\-392.3545926477\
> \189.182112099444
> \n0\x84\x00\x10\x00\x00\x001.52797639111557
> \n0\x86\x00\x10\x00\x00\x00263.433384670643
> \x0c0\x06\x00\x02\x00\x00\x002 ')
>
>
>
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