import numpy as np

morning = np.array([18, 21, 24])
evening = np.array([15, 19, 23])

by_reading = np.stack((morning, evening), axis=0)
by_city = np.stack((morning, evening), axis=-1)

print("morning shape:", morning.shape)
print("evening shape:", evening.shape)
print("by reading:")
print(by_reading)
print("by reading shape:", by_reading.shape)
print("by city:")
print(by_city)
print("by city shape:", by_city.shape)