Python function that generates random arrays of integers not working

I need to create a function that generates random arrays of integers between a and b, inclusive, where a and b define the range and M and N define the size of the output array. I've done something but it seems that it's not properly working and I don't know exactly how can I define the size of the output array, where exactly to put M and N.....Here it's my code:

import random 

def Rand(start, end, num): 
    res = [] 

    for j in range(num): 
        res.append(random.randint(start, end)) 

    return res 

# Driver Code 
num = 10
start = 20
end = 40
print(Rand(start, end, num))