To count the elements in a nested list with all elements are list

a=[[3, 4, 5,8, 8 ], [5, 6, 7], [7, 8, 9]]

def count(a):
 j=0
 n=0
 for b in a:
     j=len(b)
     n=n+j
 return n

t= count(a)
print "No elements in the nested list are:",t