Python dictionary Method - update()

The update() method is a dictionary method in Python that updates a dictionary with the key-value pairs from another dictionary, or with an iterable of key-value pairs.

The syntax for using update() is as follows:

dict.update([other])

The method takes one argument: other. other can be another dictionary or an iterable of key-value pairs.

If other is a dictionary, the update() method adds the key-value pairs from the other dictionary to the calling dictionary. If a key already exists in the calling dictionary, the value for that key is updated with the value from other.

If other is an iterable of key-value pairs, each pair is treated as a separate key-value pair to be added to the calling dictionary.

Here is an example that demonstrates the use of update():

>>> d1 = {'a': 1, 'b': 2}
>>> d2 = {'b': 3, 'c': 4}
>>> d1.update(d2)
>>> print(d1)
{'a': 1, 'b': 3, 'c': 4}

In this example, the update() method is used to update the dictionary d1 with the key-value pairs from d2. The key 'b' is present in both d1 and d2, so its value in d1 is updated to 3 to match the value in d2. The resulting dictionary is {'a': 1, 'b': 3, 'c': 4}.

Here is another example that uses an iterable of key-value pairs:

>>> d = {'a': 1, 'b': 2}
>>> d.update([('b', 3), ('c', 4)])
>>> print(d)
{'a': 1, 'b': 3, 'c': 4}

In this example, the update() method is used to update the dictionary d with an iterable of key-value pairs. The key 'b' is present in both d and the iterable, so its value in d is updated to 3. The key 'c' is not present in d, so it is added with the value 4. The resulting dictionary is {'a': 1, 'b': 3, 'c': 4}.

In summary, update() provides a way to update a dictionary with the key-value pairs from another dictionary or an iterable of key-value pairs. It can be useful in cases where you want to combine the contents of two or more dictionaries, or to add multiple key-value pairs to a dictionary at once.