:mod:`ucollections` -- collection and container types ===================================================== .. module:: ucollections :synopsis: collection and container types |see_cpython_module| :mod:`python:collections`. This module implements advanced collection and container types to hold/accumulate various objects. Classes ------- .. function:: deque(iterable, maxlen[, flags]) Deques (double-ended queues) are a list-like container that support O(1) appends and pops from either side of the deque. New deques are created using the following arguments: - *iterable* must be the empty tuple, and the new deque is created empty. - *maxlen* must be specified and the deque will be bounded to this maximum length. Once the deque is full, any new items added will discard items from the opposite end. - The optional *flags* can be 1 to check for overflow when adding items. As well as supporting `bool` and `len`, deque objects have the following methods: .. method:: deque.append(x) Add *x* to the right side of the deque. Raises IndexError if overflow checking is enabled and there is no more room left. .. method:: deque.popleft() Remove and return an item from the left side of the deque. Raises IndexError if no items are present. .. function:: namedtuple(name, fields) This is factory function to create a new namedtuple type with a specific name and set of fields. A namedtuple is a subclass of tuple which allows to access its fields not just by numeric index, but also with an attribute access syntax using symbolic field names. Fields is a sequence of strings specifying field names. For compatibility with CPython it can also be a a string with space-separated field named (but this is less efficient). Example of use:: from ucollections import namedtuple MyTuple = namedtuple("MyTuple", ("id", "name")) t1 = MyTuple(1, "foo") t2 = MyTuple(2, "bar") print(t1.name) assert t2.name == t2[1] .. function:: OrderedDict(...) ``dict`` type subclass which remembers and preserves the order of keys added. When ordered dict is iterated over, keys/items are returned in the order they were added:: from ucollections import OrderedDict # To make benefit of ordered keys, OrderedDict should be initialized # from sequence of (key, value) pairs. d = OrderedDict([("z", 1), ("a", 2)]) # More items can be added as usual d["w"] = 5 d["b"] = 3 for k, v in d.items(): print(k, v) Output:: z 1 a 2 w 5 b 3