Question

I couldn’t find anything on this subject on Google, so I think I should ask it here:

Is it possible to chain functions with Python, like jQuery does?

['my', 'list'].foo1(arg1, arg2).foo2(arg1, arg2).foo3(arg1, arg2) #etc...

I am losing a lot of space and readability when I write this code:

foo3(foo2(foo1(['my', 'list'], arg1, arg2), arg1, arg2), arg1, arg2) #etc...

There seems to exist some illusive library for creating such functions, but I can’t seem to see why this has to be so complicated-looking…

Thanks!

Answer 1

Here’s an expansion of Simon’s ListMutator suggestion:

class ListMutator(object):

    def __init__(self, seq):
        self.data = seq

    def foo1(self, arg1, arg2):
        self.data = [x + arg1 for x in self.data]
        # This allows chaining:
        return self

    def foo2(self, arg1, arg2):
        self.data = [x*arg1 for x in self.data]
        return self

if __name__ == "__main__":
    lm = ListMutator([1,2,3,4])
    lm.foo1(2, 0).foo2(10, 0)
    print lm.data

    # Or, if you really must:
    print ListMutator([1,2,3,4]).foo1(2, 0).foo2(10, 0).data

You could go one better and make ListMutator act entirely like a list by using the collections abstract base classes. In fact, you could subclass list itself, although it may restrict you from doing certain things you might need to do… and I don’t know what the general opinion is on subclassing built-in types like list.