Iterators & Generators -3

Itertools

The itertools module in the standard library provides lot of intersting tools to work with iterators.
Lets look at some of the interesting functions.
chain – chains multiple iterators together.

>>> it1 = iter([1, 2, 3])
>>> it2 = iter([4, 5, 6])
>>> itertools.chain(it1, it2)
[1, 2, 3, 4, 5, 6]

izip – iterable version of zip

>>> for x, y in itertools.izip(["a", "b", "c"], [1, 2, 3]):
...     print x, y
...
a 1
b 2
c 3

Problem 8: Write a function peep, that takes an iterator as argument and returns the first element and an equivalant iterator.

>>> it = iter(range(5))
>>> x, it1 = peep(it)
>>> print x, list(it1)
0 [0, 1, 2, 3, 4]

Problem 9: The built-in function enumerate takes an iteratable and returns an iterator over pairs (index, value) for each value in the source.

>>> list(enumerate(["a", "b", "c"])
[(0, "a"), (1, "b"), (2, "c")]
>>> for i, c in enumerate(["a", "b", "c"]):
...     print i, c
...
0 a
1 b
2 c