str.join with my types

Question

Is there opportunity to join my types using:

str.join()

I have my class:

class Slice(object):
    def __init__(self, start, end):
        self.__start = start
        self.__end = end

    def __str__(self):
        return '{0}:{1}'.format(self.__start, self.__end)

    def __repr__(self):
        return "'{}'".format(str(self))

What should i override to perform this kind of code:

','.join(Slice(1, 2), Slice(3, 4))

And get a result like this:

'1:2,3:4'

Answer 1

没有。

','.join(str(x) for x in (Slice(1, 2), Slice(3, 4)))

Answer 2

I always just do this:

','.join(map(str, (Slice(1, 2), Slice(3, 4)))

But you could also create a utility function:

def strseq(*args):
    for arg in args:
        yield str(arg)
','.join(strseq(Slice(1, 2), Slice(3, 4)))

I think this is intentional and generally a good thing: Python is strictly typed and that will shake out some silly bugs at run-time. So don't try to make the Slice a str , but instead map to str .

If you really want to go hacky, do this:

class Slice(str):
    def __init__(self, start, end):
        self.__start = start
        self.__end = end
        str.__init__('{0}:{1}'.format(self.__start, self.__end))

I keep getting an error "TypeError: str() takes at most 1 argument (2 given)" when I call str.__init__(self, 'test') in the constructor, which would normally be the correct way to do this, I think, so this is a good sign that you are not supposed to be subclassing str . But go ahead. Shoot yourself in the foot. It hurts, but in the good old-fashioned learn-something-new-a-day way :)

Answer 3

Just for the heck of it, I decided not to use any iterative function to call str(x). So here is my solution

x=(Slice(1, 2), Slice(3, 4))
','.join(['%s']*len(x)) % x