def public_key(self, sk) :
		""" compute the public key from the secret one """
		h = self.to_hash(sk)
		a = self.as_key(h)
		c = self.outer(self.B, a)
		return self.point_to_bytes(c)
 compute the public key from the secret one 
recipes/Python/579102_ed25519/recipe-579102.py