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Python Dictionary update() Function

The Dictionary update() method is used to update the dictionary with the elements from another dictionary object or from an iterable of key-value pairs.

Syntax​

my_dictionary.update(element)

update() Parameters​

Python Dictionary update() method parameters:

ParameterConditionDescription
elementOptionalA dictionary or an iterable of key:value pairs
note

If update() method is called without passing parameters, the dictionary remains unchanged.

update() Return Value​

Python Dictionary update() function does not return any value (returns None), but it modifies the dictionary in place.

Examples​

Example 1: Basic Usage of update() method in dictionary​

The update() method is generally used to merge two dictionaries.

my_dict1 = {'name': 'Tom'}
my_dict2 = {'job': 'Developer', 'age': 25}
my_dict1.update(my_dict2)

print(my_dict1) # Output: {'job': 'Dev', 'age': 25, 'name': 'Bob'}

output

{'name': 'Tom', 'job': 'Developer', 'age': 25}

When two dictionaries are merged together, existing keys are updated and new key-value pairs are added. For example, note that the value for existing key age is updated and new entry job is added.

my_dict1 = {'name': 'Tom', 'age': 25}
my_dict2 = {'job': 'Developer', 'age': 30}
my_dict1.update(my_dict2)

print(my_dict1) # Output: {'name': 'Tom', 'age': 30, 'job': 'Developer'}

output

{'name': 'Tom', 'age': 30, 'job': 'Developer'}

Example : update() with an Iterable of length two (nested list)​

The update() method accepts an iterable of key-value pairs (iterables of length two, like nested lists).

For example, let's pass an iterable of length two (nested list)

my_dict = {'name': 'Tom'}
my_dict.update([['job', 'Developer'], ['age', 25]])

print(my_dict) # Output: {'name': 'Tom', 'job': 'Developer', 'age': 25}

output

{'name': 'Tom', 'job': 'Developer', 'age': 25}

Example : update() with List of Tuples​

The update() method accepts a list of tuples.

For example:

my_dict = {'name': 'Tom'}
my_dict.update([('job', 'Developer'), ('age', 25)])

print(my_dict) # Output: {'name': 'Tom', 'job': 'Developer', 'age': 25}

output

{'name': 'Tom', 'job': 'Developer', 'age': 25}

Example : update() with Keyword Arguments​

The update() method accepts also key-value pairs as keyword arguments.

For example, let's specify key-value pairs as keyword arguments

my_dict = {'name': 'Tom'}
my_dict.update(job = 'Developer', age = 25)

print(my_dict) # Output: {'name': 'Tom', 'job': 'Developer', 'age': 25}

output

{'name': 'Tom', 'job': 'Developer', 'age': 25}

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