deque objects¶ class collections.deque ([iterable [, maxlen]]) ¶. The map() function passes each element in the list to the built-in function, a lambda function or a user-defined function, and returns the mapped object. A sequence, collection or an iterator object. In python 2 the function returns a list. Python map() Function Built-in Functions. It is mutable. 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 âdeckâ and is short for âdouble-ended queueâ). for i in F_temps: print(F_temps)