How to convert a sha256 object to integer and pack it to bytearray in python?

The simplest way in Python 2 to get the integer value of the SHA-256 digest is via the hexdigest. Alternatively, you can loop over the bytearray constructed from the binary digest. Both methods are illustrated below.

import hashlib

hashobj = hashlib.sha256('something')
val_hex = hashobj.hexdigest()
print val_hex

# Build bytearray from binary digest
val_bytes = bytearray(hashobj.digest())
print ''.join(['%02x' % byte for byte in val_bytes])

# Get integer value of digest from the hexdigest
val_int = int(val_hex, 16)
print '%064x' % val_int

# Get integer value of digest from the bytearray
n = 0
for byte in val_bytes:
    n = n<<8 | byte
print '%064x' % n

output

3fc9b689459d738f8c88a3a48aa9e33542016b7a4052e001aaa536fca74813cb
3fc9b689459d738f8c88a3a48aa9e33542016b7a4052e001aaa536fca74813cb
3fc9b689459d738f8c88a3a48aa9e33542016b7a4052e001aaa536fca74813cb
3fc9b689459d738f8c88a3a48aa9e33542016b7a4052e001aaa536fca74813cb

---

In Python 3, we can't pass a plain text string to the hashlib hash function, we must pass a bytes string or a bytearray, eg

b'something' 

or

'something'.encode('utf-8')

or

bytearray('something', 'utf-8')

We can simplify the second version to

'something'.encode()

since UTF-8 is the default encoding for str.encode (and bytes.decode()).

To perform the conversion to int, any of the above techniques can be used, but we also have an additional option: the int.from_bytes method. To get the correct integer we need to tell it to interpret the bytes as a big-endian number:

import hashlib

hashobj = hashlib.sha256(b'something')
val = int.from_bytes(hashobj.digest(), 'big')
print('%064x' % val)

output

3fc9b689459d738f8c88a3a48aa9e33542016b7a4052e001aaa536fca74813cb

The point of a bytearray is not to fit the whole content in a single cell. That's why cells are only 1 byte big.

And .digest() returns a byte string, so you are fine just using it immediately:

>>> import hashlib
>>> hashobj = hashlib.sha256('something')
>>> val = hashobj.digest()
>>> print bytearray(val)
?ɶ�E�s������5Bkz@R���6��H�
>>> print repr(bytearray(val))
bytearray(b'?\xc9\xb6\x89E\x9ds\x8f\x8c\x88\xa3\xa4\x8a\xa9\xe35B\x01kz@R\xe0\x01\xaa\xa56\xfc\xa7H\x13\xcb')