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 0x7f58297cd790>
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 0x7fa193356750>
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 0x7f766e185750>
3
4
7
13