#fourth (arange(start,stop,step))
w = np.arange(0, 10, 2)

The arange function is similar to the range function. In this example, the arange function produces points between 0 and 10 with a step of 2 exclusive of the final point. If the third argument is not provided the step=1.
w = np.arange(0, 10)
if the first and third argument are not provided. start=0 and step=1.
w = np.arange(10)
Note that unlike the range function you can use a float for steps. try
w = np.arange(0, 10, 1.5)
also try
for i in range(0,10,1.5):