append(x) Add x to the right side of the deque.

class collections.deque([iterable[, maxlen]]) Returns a new deque object initialized left-to-right (using append()) with data from iterable. If iterable is not specified, the new deque is empty. Deques are a generalization of stacks and queues (the name is pronounced “deck” and is short for “double-ended queue”). Deques support thread-safe, memory efficient appends and pops from either side of the deque with approximately the same O(1) performance in either direction. Though list objects sup

__missing__(key) If the default_factory attribute is None, this raises a KeyError exception with the key as argument. If default_factory is not None, it is called without arguments to provide a default value for the given key, this value is inserted in the dictionary for the key, and returned. If calling default_factory raises an exception this exception is propagated unchanged. This method is called by the __getitem__() method of the dict class when the requested key is not found; whatever

default_factory This attribute is used by the __missing__() method; it is initialized from the first argument to the constructor, if present, or to None, if absent.

class collections.defaultdict([default_factory[, ...]]) Returns a new dictionary-like object. defaultdict is a subclass of the built-in dict class. It overrides one method and adds one writable instance variable. The remaining functionality is the same as for the dict class and is not documented here. The first argument provides the initial value for the default_factory attribute; it defaults to None. All remaining arguments are treated the same as if they were passed to the dict constructor

update([iterable-or-mapping]) Elements are counted from an iterable or added-in from another mapping (or counter). Like dict.update() but adds counts instead of replacing them. Also, the iterable is expected to be a sequence of elements, not a sequence of (key, value) pairs.

subtract([iterable-or-mapping]) Elements are subtracted from an iterable or from another mapping (or counter). Like dict.update() but subtracts counts instead of replacing them. Both inputs and outputs may be zero or negative. >>> c = Counter(a=4, b=2, c=0, d=-2) >>> d = Counter(a=1, b=2, c=3, d=4) >>> c.subtract(d) >>> c Counter({'a': 3, 'b': 0, 'c': -3, 'd': -6}) New in version 3.2.

most_common([n]) Return a list of the n most common elements and their counts from the most common to the least. If n is omitted or None, most_common() returns all elements in the counter. Elements with equal counts are ordered arbitrarily: >>> Counter('abracadabra').most_common(3) [('a', 5), ('r', 2), ('b', 2)]

fromkeys(iterable) This class method is not implemented for Counter objects.

elements() Return an iterator over elements repeating each as many times as its count. Elements are returned in arbitrary order. If an element’s count is less than one, elements() will ignore it. >>> c = Counter(a=4, b=2, c=0, d=-2) >>> sorted(c.elements()) ['a', 'a', 'a', 'a', 'b', 'b']