python answer please

Write a function, dot Product (1sti, ist2), which returns the dot product of two list. The dot product takes two equal length sequences of numbers and returns the sum of the products of the corresponding entries of the two sequences of numbers. For example, dot Product ([2,3,4], [1,2,3]), returns 20. That's 2*1+3*2+4*3 = 20. If the list have different sizes then the function should return None. A correct solution does not use any Python modules (e.g., Numpy), any of the the following functions sum(), zip, map() or lambda functions