问如何追加数组以避免越界索引？

EN

def simple_model_test():

    labda, mu, Days = 10, 4, 10
    a = poisson(labda).rvs(Days)            # Generate array with number of arrivals each day
    s = np.ones_like(a) * mu                # Generate equal sizes array with time slots
    s = np.append(s, np.ones_like(a) * mu)  # Add some additional days at the end of time horizon

    for i in range(0, len(a)):              # Cycle through all days of time horizon
        j = i + 1                           # Patients cannot be served at day of arrival
        # if s[j] is empty:                   # I was trying to do something like this, but this does not work
           # s = np.append(s, mu)
        while a[i] > 0:                     # Assign all patients that arrived to a time slot
            if s[j] > 0:                    # Check if time slots are available at day j
                a[i] -= 1                   # To indicate that a patient is assigned
                s[j] -= 1                   # To indicate that a time slot is filled at day j
            else:
                j += 1                      # Check for free time slots next day
    print(s)

simple_model_test()