I have a list of integer ASCII values that I need to transform into a string (binary) to use as the key for a crypto operation. (I am re-implementing java crypto code in python)
This works (assuming an 8-byte key):
key = struct.pack('BBBBBBBB', 17, 24, 121, 1, 12, 222, 34, 76)
However, I would prefer to not have the key length and unpack() parameter list hardcoded.
How might I implement this correctly, given an initial list of integers?
Thanks!
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I much prefer the array module to the struct module for this kind of tasks (ones involving sequences of homogeneous values):
>>> import array
>>> array.array('B', [17, 24, 121, 1, 12, 222, 34, 76]).tostring()
'\x11\x18y\x01\x0c\xde"L'
no len call, no string manipulation needed, etc -- fast, simple, direct, why prefer any other approach?!
Shorter version of previous using map() function (works for python 2.7):
"".join(map(chr, myList))
This is reviving an old question, but in Python 3, you can just use bytes directly:
>>> bytes([17, 24, 121, 1, 12, 222, 34, 76])
b'\x11\x18y\x01\x0c\xde"L'
key = "".join( chr( val ) for val in myList )
struct.pack('B' * len(integers), *integers)
*sequence means "unpack sequence" - or rather, "when calling f(..., *args ,...), let args = sequence".
For Python 2.6 and later if you are dealing with bytes then a bytearray is the most obvious choice:
>>> str(bytearray([17, 24, 121, 1, 12, 222, 34, 76]))
'\x11\x18y\x01\x0c\xde"L'
To me this is even more direct than Alex Martelli's answer - still no string manipulation or len call but now you don't even need to import anything!
Source: Stackoverflow.com