Question :
Has Python 3 to_bytes been back-ported to python 2.7?
This is the function I’m after: –
http://docs.python.org/3/library/stdtypes.html#int.to_bytes
I need big endianness support.
Answer #1:
Based on the answer from @nneonneo, here is a function that emulates the to_bytes API:
def to_bytes(n, length, endianess='big'):
h = '%x' % n
s = ('0'*(len(h) % 2) + h).zfill(length*2).decode('hex')
return s if endianess == 'big' else s[::-1]
Answer #2:
To answer your original question, the to_bytes
method for int
objects was not back ported to Python 2.7 from Python 3. It was considered but ultimately rejected. See the discussion here.
Answer #3:
To pack arbitrary-length long
s in Python 2.x, you can use the following:
>>> n = 123456789012345678901234567890L
>>> h = '%x' % n
>>> s = ('0'*(len(h) % 2) + h).decode('hex')
>>> s
'x01x8exe9x0fxf6xc3sxe0xeeN?nxd2'
This outputs the number in big-endian order; for little endian, reverse the string (s[::-1]
).
Answer #4:
You can probably use struct.pack
instead:
>>> import struct
>>> struct.pack('>i', 123)
'x00x00x00{'
It doesn’t do arbitrary lengths in the way int.to_bytes
does, but I doubt you need that.