Secret Recipes of the Python Ninja

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. If last is not provided or manually set to True, then the ...