Call int() function on every list element in Python

Question

I have a list with numeric strings, like so:

numbers = ['1', '5', '10', '8'];

I would like to convert every list element to integer, so it would look like this:

numbers = [1, 5, 10, 8];

I could do it using a loop, like so:

new_numbers = [];
for n in numbers:
    new_numbers.append(int(n));
numbers = new_numbers;

Does it have to be so ugly? I'm sure there is a more pythonic way to do this in a one line of code. Please help me out.

Answer 1

This is what list comprehensions are for:

numbers = [ int(x) for x in numbers ]

Answer 2

In Python 2.x another approach is to use map:

numbers = map(int, numbers)

Note: in Python 3.x map returns a map object which you can convert to a list if you want:

numbers = list(map(int, numbers))

Answer 3

Another way,

for i, v in enumerate(numbers): numbers[i] = int(v)

Answer 4

If you are intending on passing those integers to a function or method, consider this example:

sum(int(x) for x in numbers)

This construction is intentionally remarkably similar to list comprehensions mentioned by adamk. Without the square brackets, it's called a generator expression, and is a very memory efficient way of passing a list of arguments to a method. A good discussion is available here: http://stackoverflow.com/questions/47789/generator-expressions-vs-list-comprehension

Answer 5

just a point,

numbers = [int(x) for x in numbers]

this way is more natural for us, while

number = map(int, x)

is more fast.

Probably this will not matter in most cases