Add a new item to a dictionary in Python [duplicate]

default_data['item3'] = 3

Easy as py.

Another possible solution:

default_data.update({'item3': 3})

which is nice if you want to insert multiple items at once.

It can be as simple as:

default_data['item3'] = 3

As Chris' answer says, you can use update to add more than one item. An example:

default_data.update({'item4': 4, 'item5': 5})

Please see the documentation about dictionaries as data structures and dictionaries as built-in types.

It occurred to me that you may have actually be asking how to implement the + operator for dictionaries, the following seems to work:

>>> class Dict(dict):...     def __add__(self, other):...         copy = self.copy()...         copy.update(other)...         return copy...     def __radd__(self, other):...         copy = other.copy()...         copy.update(self)...         return copy... >>> default_data = Dict({'item1': 1, 'item2': 2})>>> default_data + {'item3': 3}{'item2': 2, 'item3': 3, 'item1': 1}>>> {'test1': 1} + Dict(test2=2){'test1': 1, 'test2': 2}

Note that this is more overhead then using dict[key] = value or dict.update(), so I would recommend against using this solution unless you intend to create a new dictionary anyway.