index in zip python

alist = ['a1', 'a2', 'a3']
blist = ['b1', 'b2', 'b3']

for i, (a, b) in enumerate(zip(alist, blist)):
    print i, a, b

for index, (value1, value2) in enumerate(zip(data1, data2)):
    print(index, value1 + value2)  # for Python 2 use: `print index, value1 + value2` (no braces)