It. A handy iterator with method chaining.

it.py

import itertools
import functools

class It:
    """A handy iterator with method chaining.
    
    >>> It([1, 2, 3]).map(lambda x: x**2).filter(lambda x: x<5).chain_after('abc').apply(list)
    ['a', 'b', 'c', 1, 4]
    
    """
    def __init__(self, iterable):
        self._it = iter(iterable)

    def __iter__(self):
        return self._it

    def reduce(self, fn, initializer=None):
        if initializer is not None:
            return functools.reduce(fn, self, initializer)
        return functools.reduce(fn, self)

    def map(self, *fns):
        return It(fns).reduce(lambda it, fn: It(map(fn, it)), self)

    def starmap(self, *fns):
        return It(fns).reduce(lambda it, fn: It(itertools.starmap(fn, it)), self)

    def filter(self, *fns):
        return It(fns).reduce(lambda it, fn: It(filter(fn, it)), self)

    def apply(self, *fns):
        return It(fns).reduce(lambda it, fn: fn(it), self)

    def apply_it(self, *fns):
        return It(fns).reduce(lambda it, fn: It(fn(it)), self)

    def chain(self, *iterables):
        return It(itertools.chain(self, *iterables))

    def chain_after(self, *iterables):
        return It(itertools.chain(*iterables, self))