Basic question

[Alex Martelli]

Cesar G. Miguel <cesar.gomes at gmail.com> wrote:

> On May 12, 3:40 pm, Dmitry Dzhus <m... at sphinx.net.ru> wrote:
> > > Actually I'm trying to convert a string to a list of float numbers:
> > > str = '53,20,4,2' to L = [53.0, 20.0, 4.0, 2.0]
> >
> > str="53,20,4,2"
> > map(lambda s: float(s), str.split(','))
> >
> > Last expression returns: [53.0, 20.0, 4.0, 2.0]
> > --
> > Happy Hacking.
> >
> > Dmitry "Sphinx" Dzhushttp://sphinx.net.ru
> 
> Nice!

As somebody else alredy pointed out, the lambda is supererogatory (to
say the least).


> The following also works using split and list comprehension (as
> suggested in a brazilian python forum):
> 
> -------------------
> L = []
> file = ['5,1378,1,9', '2,1,4,5']
> str=''
> for item in file:
>       L.append([float(n) for n in item.split(',')])

The assignment to str is useless (in fact potentially damaging because
you're hiding a built-in name).

L = [float(n) for item in file for n in item.split(',')]

is what I'd call Pythonic, personally (yes, the two for clauses need to
be in this order, that of their nesting).


Alex