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I want to add an item to an existing dictionary in Python. For example, this is my dictionary:
default_data = {
'item1': 1,
'item2': 2,
}
I want to add a new item such that:
default_data = default_data + {'item3':3}
How can I achieve this?
3 Answers
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.
