What is the easiest way to convert list with str into list with int?

Question

What is the easiest way to convert list with str into list with int in Python? For example, we have to convert ['1', '2', '3'] to [1, 2, 3]. Of course, we can use a for loop, but it's too easy.

Answer 1

Python 2.x:

map(int, ["1", "2", "3"])

Python 3.x (in 3.x, map returns an iterator, not a list as in 2.x):

list(map(int, ["1", "2", "3"]))

map documentation: 2.6, 3.1

Answer 2

[int(i) for i in str_list]

Answer 3

You could also use list comprehensions:

new = [int(i) for i in old]

Or the map() builtin function:

new = map(int, old)

Or the itertools.imap() function, which will provide a speedup in some cases but in this case just spits out an iterator, which you will need to convert to a list (so it'll probably take the same amount of time):

import itertools as it
new = list(it.imap(int, old))

Answer 4

If your strings are not only numbers (ie. u''), you can use :

new = [int(i) for i in ["1", "2", "3"] if isinstance(i, int) or isinstance(i, (str, unicode)) and i.isnumeric()]

Answer 5

If It is array and has installed numpy. We can used below code as well.

import numpy as np

np.array(['1', '2', '3'],dtype=int)