DES(p,k) == ~DES(~p,~k)

desnot.py

#!/usr/bin/python3

from Crypto.Cipher import DES
import os
from binascii import hexlify

def bitwise_not(buf):
	return bytes([ (~b) & 0xff for b in buf ])

def print_hex(name, value):
	value = str(hexlify(value), "utf-8")
	print("{0:s}\t{1:s}".format(name, value))

key = os.urandom(8)
plain = os.urandom(8)

notkey = bitwise_not(key)
notplain = bitwise_not(plain)

cipher = DES.new(key, DES.MODE_ECB).encrypt(plain)
notcipher = DES.new(notkey, DES.MODE_ECB).encrypt(notplain)

print_hex(" Ciphertext", cipher)
print_hex("~Ciphertext", notcipher)
print_hex("|Ciphertext", bytes([ cipher[i] | notcipher[i] for i in range(8)]))
print_hex("&Ciphertext", bytes([ cipher[i] & notcipher[i] for i in range(8)]))