Python 3 reference · Dictionary Methods

Python Dictionary update() Method

Add or overwrite keys from another mapping, an iterable of pairs, or keyword arguments, in place.

Syntax

dict.update(other=(), /, **kwargs)

Parameter	Description
`other` optional	A mapping or an iterable of `(key, value)` pairs.
`**kwargs` optional	More keys as keyword arguments.

None.

Merge in placeTry it yourself

settings = {"theme": "light", "lang": "en"}
settings.update({"theme": "dark"}, size=14)
print(settings)

Output

{'theme': 'dark', 'lang': 'en', 'size': 14}

The | and |= operatorsTry it yourself

base = {"a": 1}
print(base | {"b": 2}, base)   # new dict (3.9+)
base |= {"c": 3}             # in place, like update()
print(base)

Output

{'a': 1, 'b': 2} {'a': 1}
{'a': 1, 'c': 3}

Version	Change
Python 3.0	Added

dict.setdefault() · Return the value for a key; if the key is missing, insert it with a default value first and return that.
dict.copy() · Return a shallow copy of the dictionary: a new dict with the same keys and values (nested values are shared).
dict() · Create a dictionary: a mapping of keys to values. Build it from keyword arguments, pairs or another mapping.
Python Dictionaries · tutorial