The usage of np.random.seed

According to What does numpy.random.seed(0) do?, we understand the usage concept of this code.

But, How we can understand what value is appropriate for seed? For example, in http://emcee.readthedocs.io/en/latest/tutorials/line/ we can see the value (123) and (42). np.random.seed(123) and np.random.seed(42). is it based on specific principle?

I appreciate your help and your attention.