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, Dec 03 '15 at 17:49
You can pull integers out of binary using the `struct` module. — tdelaney, Dec 03 '15 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, Dec 03 '15 at 17:51
Possible duplicate of [Convert hex string to int in Python](http://stackoverflow.com/questions/209513/convert-hex-string-to-int-in-python) — Joseph Farah, Dec 03 '15 at 18:00

Mark Tolonen · Accepted Answer · 2015-12-03T18:07:27.450

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 03 '15 at 18:07

answered Dec 03 '15 at 17:53

Mark Tolonen

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you sure it's unsigned? – Chad S. Dec 03 '15 at 17:54
@Chad, Nope, just as I am unsure if it is big- or little-endian. – Mark Tolonen Dec 03 '15 at 17:54
OP converted hex to binary.... I assume in the same program so I'm betting on native format `"@QQ"`. – tdelaney Dec 03 '15 at 17:56
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.... – Mark Tolonen Dec 03 '15 at 17:59

score 0 · Answer 2 · answered Dec 03 '15 at 17:57

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 03 '15 at 17:57

Jas

327
2
9

Good answer but 5 minutes too late. This answer has already been posted. – tdelaney Dec 03 '15 at 17:59

Binary Data in Python

2 Answers2