Binary Data in Python

Question

I have a string of binary I'm trying to convert to ints. The chunks were originally 8 hex chars each and converted into binary. How do you turn it into its 64-bit int value?

s = 'Q\xcb\x80\x80\x00\x00\x01\x9bQ\xcc\xd2\x00\x00\x00\x01\x9b'
date_chunk = s[0:8]
value_chunk = s[8:]

Looks like hex now that I got it to print. How do I make two ints? The first is a date encoded to seconds since epoch.

That isn't a valid Python statement. Show some real code with expected and received results, and Python version used. — Mark Tolonen
– Mark Tolonen, Commented Dec 3, 2015 at 17:49
You can pull integers out of binary using the struct module. — tdelaney
– tdelaney, Commented Dec 3, 2015 at 17:50
How was the original data translated to binary? Do you have the code which performs it? It's impossible to know how to convert it back without knowing the encoding. — interjay
– interjay, Commented Dec 3, 2015 at 17:51

Mark Tolonen · Accepted Answer · 2015-12-03 18:07:27Z

4

The struct module unpacks binary. Use qq for signed ints.

>>> s = 'Q\xcb\x80\x80\x00\x00\x01\x9bQ\xcc\xd2\x00\x00\x00\x01\x9b'
>>> len(s)
16
>>> import struct
>>> struct.unpack('>QQ',s) # big-endian
(5893945824588595611L, 5894316909762970011L)
>>> struct.unpack('<QQ',s) # little-endian
(11169208553011465041L, 11169208550869355601L)

You also mentioned an original 8 hex chars. Use the binascii.unhexlify function in that case. Example:

>>> s = '11223344'
>>> import binascii
>>> binascii.unhexlify(s)
'\x11"3D'
>>> struct.unpack('>L',binascii.unhexlify(s))
(287454020,)
>>> hex(287454020)
'0x11223344'

edited Dec 3, 2015 at 18:07

answered Dec 3, 2015 at 17:53

Mark Tolonen

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4 Comments

Chad S. Over a year ago

you sure it's unsigned?

Mark Tolonen Over a year ago

@Chad, Nope, just as I am unsure if it is big- or little-endian.

tdelaney Over a year ago

OP converted hex to binary.... I assume in the same program so I'm betting on native format "@QQ".

Mark Tolonen Over a year ago

Both numbers seem quite large for seconds since an epoch, but if the OP wants to tell us what the expected date should be and what epoch it is based....

Jas · Accepted Answer · 2015-12-03 17:57:17Z

0

import struct
struct.unpack(">QQ",s)

Or

struct.unpack("<QQ",s)

Depending on the endianness of the machine that generated the bytes

answered Dec 3, 2015 at 17:57

Jas

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1 Comment

tdelaney Over a year ago

Good answer but 5 minutes too late. This answer has already been posted.

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