Python itertools imap examples

Python itertools imap is efficient way of mapping and looping over a large iterable. Here is the usage for imap:

itertools.imap(function, *iterables)

The function should take one or more arguments (depending upon how many iterables are passed) and should return new value.

Here are some examples.

itertools imap with function on one list

Given a list of numbers get a new list with items squared using function.

import itertools
def square(x):
  return x*x
a = [1,2,4,10]
b = itertools.imap(square, a)
print b
for i in b:
  print i

<itertools.imap object at 0x7f8535eb8790>
1
4
16
100

itertools imap with lambda one one list

Given a list of numbers get a new list with items squared using lambda.

import itertools
a = [1,2,4,10]
b = itertools.imap(lambda  x: x*x, a)
print b
for i in b:
  print i

<itertools.imap object at 0x7fd89ea54750>
1
4
16
100

itertools imap on two lists

Given two lists of numbers get a new list where items are sum of items from these two lists.

import itertools
a = [1,2,4,10]
b = [2,2,3,3]
new = itertools.imap(lambda  x, y: x+y, a, b)
print new
for i in new:
  print i

<itertools.imap object at 0x7efcab10a750>
3
4
7
13