Python and arrays

Question

I know that python is a crazy language because of it's cycles constructions :)

So, I have an array of numbers but in string type:

a = ['1', '40', '356', '...']

I need this or a copy of this array but with float type instead of string. The only thing is that the code should be in one line.

Help me, please :)

Felix Kling · Accepted Answer · 2011-06-18T14:49:21.323

11

b = map(float, a)

edited Jun 18 '11 at 14:49

answered Jun 18 '11 at 14:41

Felix Kling

3

this is one of the few cases where map/reduce are cleaner than comprehensions – Gabi Purcaru Jun 18 '11 at 14:43
@Gabi: Exactly, using `map` with built-in functions usually beats (list) comprehension. – Felix Kling Jun 18 '11 at 14:45
Great answer :) I love python. Thanks – Max Frai Jun 18 '11 at 14:53
but `map` returns a iterator on python3... So you'll have to change the code when migrating. A list comprehension will always work – JBernardo Jun 18 '11 at 15:25
2to3 will take care of that. Porting without it is crazy talk (except perhaps some very rare circumstances) anyway. – Jun 18 '11 at 15:28
@delnan of course 2to3 will fix it. It will fix all `map(func, it)` to `list(map(func, it))` which is pretty bad – JBernardo Jun 18 '11 at 15:31

Steve Mayne · Answer 2 · 2011-06-18T17:18:29.470

8

 a = ['1', '40', '356', '...']
 b = [float(x) for x in a]

This is called a list comprehension. It's a very powerful feature of Python, and you can read more about list comprehensions here:

edited Jun 18 '11 at 17:18

answered Jun 18 '11 at 14:41

Steve Mayne

2 Answers2