I want to batch convert the result of "string" .split () in Python

Like this

a, b, c = "hello 3.14 0".split()
b = float(b)
c = int(c)

It's a hassle, so I want a way to do it in one shot ... Maybe everyone is reinventing the wheel, right?

@Odashi_t on twitter

The process of reading lines in Python, separating them with spaces, and reading values in each variable, always a,b,c,d,e,... = line.split() After that, I've converted each one, but is there any easy way to write it?

I don't need anything as sophisticated as a regular expression, so a,b,c,d,e = split_and_convert(line, (int, float, str, str, int)) I'd be happy if I could write something like>.

I also wanted to know your smart way, so I will post the one I am using

def map_apply(proc, args):
    # return [f(x) for f, x in zip(proc, args)]
    return map(lambda f,x:f(x), proc, args)  # map(apply, proc, args) doesn't work like this

class FieldConverter:
    def __init__(self, *args):
        self._converters = args
        def conv_proc(f):
            def _wrap(conv_proc_to_num):
                def proc(x):
                    try:
                        return conv_proc_to_num(x)
                    except ValueError:
                        return 0
                return proc
            if f is None:
                return lambda s:s  # identity
            elif isinstance(f, str):
                return lambda s:s.decode(f)  # -> unicode
            elif f in (int, float):
                return _wrap(f)
            else:
                return f
        if len(args) > 0:
            self.converters = [conv_proc(f) for f in self._converters]
        else:
            self.converters = None

    def convert(self, fields):
        if self.converters:
            return map_apply(self.converters, fields)
        else:
            return fields


def test_map_apply():
    assert [0, -1, 3.14, 5.0] == map_apply([int,int,float,float], ['0','-1','3.14','5'])
    assert [0,u'Japanese','Japanese'] == map_apply([int,lambda s:s.decode('utf-8'),lambda s:s], ['0','Japanese','Japanese'])

def test_field_converter():
    assert [0, -1, 3.14, 5.0] == FieldConverter(int,int,float,float).convert(['0','-1','3.14','5'])
    assert [0,u'Japanese','Japanese'] == FieldConverter(int,'utf-8',None).convert(['0','Japanese','Japanese'])

I don't need to explain int and float. If you do'utf-8', it will be decoded in UTF-8 and converted to unicode. None is no conversion You can pass any one-variable function (even lambda).

@ odashi_t's split_and_convert ()

def split_and_convert(line, types, delim=' '):
    field_converter = FieldConverter(*types)
    return field_converter.convert(line.split(delim))

def test_split_and_convert():
    assert [0, -1, 3.14, 5.0] == split_and_convert('0\t-1\t3.14\t5', (int,int,float,float), '\t')
    assert [0, u'Japanese', 'Japanese'] == split_and_convert('0,Japanese,Japanese', (int,'utf-8',None), ',')

I wonder if it can be implemented like this. I want to cache field_converter.

If the conversion is just an int or float

def split_and_convert(line, types, delim=' '):
    return [f(x) for f,x in zip(types, line.split(delim))]

It's okay though.

If this

a, b, c, d = split_and_convert('0\t-1\t3.14\t5', (int,int,float,float), '\t')

Can be used like. (A = 0, b = -1, t = 3.14, d = 5.0)

For the time being, I will put the code on gist https://gist.github.com/naoyat/3db8cd96c8dcecb5caea