Implementing OrderedDict
Like Counter, the OrderedDict is a dictionary subclass the doesn't randomize the order of dictionary items. As items are added to the OrderedDict, it remembers the order that the keys were inserted and maintains that order. Even if a new entry overwrites an existing key, the position within the dictionary doesn't change. However, if an entry is deleted, re-inserting it will place it at the end of the dictionary.
OrderedDict, being a subclasses of dict, inherit all the methods available to dictionaries. There are also three special methods available to OrderedDict:
popitem(last=True): It returns and removes the key:value pair at the end of the dictionary. Iflastis not provided or manually set toTrue, then the popped value is LIFO (last in, first out). Iflastis set toFalse, then the popped value is FIFO.move_to_end(key, last=True): It moves the provided key to the end of the dictionary. Iflastis set toTrue, then the key moves to the right. Iflastis set to...
