# -*- coding: utf-8 -*-

"""Сравнение скорости доступа к глобальным, локальным переменным
   и атрибумам объекта."""

class xrange_class(object):
    """xrange_class([start = 0], end, [step = 1])"""
    def __init__(self, start_or_stop, end = None, step = 1):
        if end is None:
            start, end = 0, start_or_stop
        else:
            start = start_or_stop
        self.start = start
        self.end = end
        self.step = step

        # Вычисляем количество членов последовательности 
        if start < end and step < 0:
            self.len = 0
        elif start > end and step > 0:
            self.len = 0
        elif start == end:
            self.len = 0
        elif step == 0:
            raise ValueError("xrange() step argument must not be zero")
        else:
            self.len = abs((end - start) / step)

        # Максимальный и минимальный (отрицательный) индексы
        self.max_index = self.len - 1
        self.min_index = self.len * (-1)

    def __iter__(self):
        """Плюс этого метода не только в скорости, но и в потокозащите."""
        start, step, len = self.start, self.step, self.len
        n = 0
        while n < len:
            yield start + step * n
            n += 1
        raise StopIteration


# Это я перегрузил для чистоты эксперимента
class xrange_class_locals(xrange_class):
    def __iter__(self):
        start, step, len = self.start, self.step, self.len
        n = 0
        while n < len:
            yield start + step * n
            n += 1
        raise StopIteration


start = step = len = 0
class xrange_class_globals(xrange_class):
    def __iter__(self):
        global start
        global step
        global len
        start, step, len = self.start, self.step, self.len
        n = 0
        while n < len:
            yield start + step * n
            n += 1
        raise StopIteration


class xrange_class_attrs(xrange_class):
    def __iter__(self):
        n = 0
        while n < self.len:
            yield self.start + self.step * n
            n += 1
        raise StopIteration


if __name__ == '__main__':
    import timeit
    NUM = 10

    timer_xrange_class_locals = timeit.Timer('for x in xrange_class_locals(1000000): pass',
                                             'from __main__ import xrange_class_locals')
    print "locals:  %5.3f" % timer_xrange_class_locals.timeit(NUM)


    timer_xrange_class_globals = timeit.Timer('for x in xrange_class_globals(1000000): pass',
                                              'from __main__ import xrange_class_globals')
    print "globals: %5.3f" % timer_xrange_class_globals.timeit(NUM)


    timer_xrange_class_attrs = timeit.Timer('for x in xrange_class_attrs(1000000): pass',
                                            'from __main__ import xrange_class_attrs')
    print "attrs:   %5.3f" % timer_xrange_class_attrs.timeit(NUM)


    timer_xrange = timeit.Timer('for x in xrange(1000000): pass')
    print "xrange:  %5.3f  :-)" % timer_xrange.timeit(NUM)