### How to use Python's enumerate and zip to iterate over two lists and their indices.

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**enumerate**- Iterate over indices and items of a list

The Python Cookbook (Recipe 4.4) describes how to iterate over items and indices in a list using

`enumerate`

. For example:
alist = ['a1', 'a2', 'a3'] for i, a in enumerate(alist): print i, ayields:

0 a1 1 a2 2 a3

**zip**- Iterate over two lists in parallel

I previously wrote about using

`zip`

to iterate over two lists
in parallel. Example:
alist = ['a1', 'a2', 'a3'] blist = ['b1', 'b2', 'b3'] for a, b in zip(alist, blist): print a, byields:

a1 b1 a2 b2 a3 b3

**enumerate with zip**

Here is how to iterate over two lists and their indices using enumerate together with zip:

alist = ['a1', 'a2', 'a3'] blist = ['b1', 'b2', 'b3'] for i, (a, b) in enumerate(zip(alist, blist)): print i, a, byields:

0 a1 b1 1 a2 b2 2 a3 b3

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