Numpy Upsamle np.array /increase size of np.array by adding mean value of cosecuitive elements

I have an np.array which I need to make its size double/triple/quadruple. I want to do it by adding 1/2/3 elements between every 2 consecutive elements.
for example:

np.array([1,2,3,4,5])

to be

np.array([1,1.5,2,2.5,3,3.5,4,4.5,5,5.5])

There is no problem doing that using python. but I need the fastest possible way, preferably using Numpy/Scipy.

>Solution :

np.interp:

a = np.array([1,2,3,4,5])
ur = 2  # upsample rate
np.interp(np.arange((len(a)-1)*ur+1)/ur, xp=np.arange(len(a)), fp=a)
# output: array([1. , 1.5, 2. , 2.5, 3. , 3.5, 4. , 4.5, 5.])