Convert a Python int into a big-endian string of bytes

In Python 3.2+, you can use int.to_bytes:

If you don’t want to specify the size

>>> n = 1245427
>>> n.to_bytes((n.bit_length() + 7) // 8, 'big') or b'\0'
b'\x13\x00\xf3'

If you don’t mind specifying the size

>>> (1245427).to_bytes(3, byteorder="big")
b'\x13\x00\xf3'