Python: How do I convert an array of strings to an array of numbers?

Question

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

current array: ['1','-1','1'] desired array: [1,-1,1]

Why do you call 'array' what are lists ? See: (http://docs.python.org/library/array.html#module-array) — eyquem, Mar 15 '11 at 01:33
MATHY people call Python lists an array. A 2-d list/array is a matrix. I believe the origin is from linear algebra. — James VB, Feb 20 '22 at 22:23

score 82 · Accepted Answer · answered Mar 15 '11 at 00:06

82

Use int which converts a string to an int, inside a list comprehension, like this:

desired_array = [int(numeric_string) for numeric_string in current_array]

answered Mar 15 '11 at 00:06

sepp2k

Worth noting that you can use this method for casting to a class as well, e.g. `for instance in [MyClass(name) for name in list_of_names]:` – brandonscript Dec 30 '17 at 00:19
The OP said numbers... so a better answer would be `[float(x) for x in current_array]` which also handles non-integer values – John Henckel Dec 27 '21 at 15:52

score 58 · Answer 2 · edited May 23 '21 at 18:11

58

List comprehensions are the way to go (see @sepp2k's answer). Possible alternative with map:

list(map(int, ['1','-1','1']))

edited May 23 '21 at 18:11

Vimal Kumar

answered Mar 15 '11 at 00:07

miku

2

A perfect example why declarative style might be much better than imperative IMHO. – Piohen Jul 09 '14 at 09:25
It however does not return a list, but a map. At least after I did x = map(int, ['1','-1','1']) I could not call len(x). – maxauthority May 11 '21 at 09:49

score 0 · Answer 3 · answered Mar 15 '11 at 00:08

0

Let's see if I remember python

list = ['1' , '2', '3']
list2 = []
for i in range(len(list)):
    t = int(list[i])
    list2.append(t)

print list2

edit: looks like the other responses work out better

answered Mar 15 '11 at 00:08

Duniyadnd

3 Answers3