method chaining in python

Question

(not to be confused with itertools.chain)

I was reading the following: http://en.wikipedia.org/wiki/Method_chaining

My question is: what is the best

Answer 1

It's possible if you use only pure functions so that methods don't modify self.data directly, but instead return the modified version. You also have to return Chainable instances.

Here's an example using collection pipelining with lists:

import itertools

try:
    import builtins
except ImportError:
    import __builtin__ as builtins


class Chainable(object):
    def __init__(self, data, method=None):
        self.data = data
        self.method = method

    def __getattr__(self, name):
        try:
            method = getattr(self.data, name)
        except AttributeError:
            try:
                method = getattr(builtins, name)
            except AttributeError:
                method = getattr(itertools, name)

        return Chainable(self.data, method)

    def __call__(self, *args, **kwargs):
        try:
            return Chainable(list(self.method(self.data, *args, **kwargs)))
        except TypeError:
            return Chainable(list(self.method(args[0], self.data, **kwargs)))

Use it like this:

chainable_list = Chainable([3, 1, 2, 0])
(chainable_list
    .chain([11,8,6,7,9,4,5])
    .sorted()
    .reversed()
    .ifilter(lambda x: x%2)
    .islice(3)
    .data)
>> [11, 9, 7]

Note that .chain refers to itertools.chain and not the OP's chain.