Lock step iteration in Python

Today I will log this big feature in python 2.x.That is lock set iteration.so what's that?let's assume,we have two list and for some reason we want to iteration them in the same time.In other language(eg.Java).we need a nesting loop.But in python .we can use map function,it's build-in.following code is a example.
>>a=(1,2,3)
>>b=(4,5,6)
>>for i in map(None,a,b): print i
The result is :
(1, 4)
(2, 5)
(3, 6)
Wow.It's cool ,right.now assume the length of each list is different.for example,we set them like this
>>a=(1,2,3)
>>b=(4,5,6,7,8)
The result is:
(1, 4)
(2, 5)
(3, 6)
(None, 7)
(None, 8)

As you can see,now we have two extra small list with the element None.Yes,Python auto append a None type in last list,because it is the first parameter in the map function.Until now,it looks good ,right ?we only write one line code ,then map function do two times loop.But it's not elegant.because :

 - It is non-obvious to programmers without a functional
     programming background.
   - The use of the magic `None' first argument is non-obvious.
   - It has arbitrary, often unintended, and inflexible semantics
     when the lists are not of the same length: the shorter sequences
     are padded with `None'.

Fortunately,we have another function,zip.yes it's good to use.let me give a example:
>>a=(1,2,3)
>>b=(4,5,6,7,8)
>>zip(a,b)
The result is:
(1, 4)
(2, 5)
(3, 6)
Yes,as you can see,no other two redundant list.it's more clearly.of course,if you think that
other twos is useful,you can also use the map function.But now we have another choose.