How to unpack binary formatted dates in python?

Question

In a database export file i have a column with dates which are stored in binary format. I'm trying to unpack dates in the file so that "\\x07\\xdb\\x0c\\x01" becomes "01-12-2011" again.

I know how the hexadecimal values corresspond to their decimal counterpart,

0x07DB = 2011
0x0C = 12
0x01 = 01

But how to properly unpack these formatted dates?

Answer 1

Use the struct module to unpack these values to a tuple of integers:

import struct
year, month, day = struct.unpack('>HBB', "\x07\xdb\x0c\x01")

The >HBB format specifier tells struct to expect 3 values in little endian format, one unsigned short (a 2 byte value, read as an integer) and to unsigned chars (1 byte values, read as integers).

You could then pass these to datetime.date() to create a date object if you want:

from datetime import date
import struct

somedate = date(*struct.unpack('>HBB', "\x07\xdb\x0c\x01"))

Demo:

>>> import struct
>>> from datetime import date
>>> date(*struct.unpack('>HBB', "\x07\xdb\x0c\x01"))
datetime.date(2011, 12, 1)

or you could use string formatting:

>>> '{2:02d}-{1:02d}-{0}'.format(*struct.unpack('>HBB', "\x07\xdb\x0c\x01"))
'01-12-2011'

to create a string representing that date.