How to Update the Value for a Key in a Dictionary in Python

How to Update the Value for a Key in a Dictionary in Python ?

Answer

To update the value for a key in a dictionary in Python, you can use key assignment or the `update` method. If the key does not exist, it will be added to the dictionary with the specified value.

✐ Examples

1 Updating the Value for a Key Using Key Assignment

We can update the value for a key in a dictionary in Python using key assignment. This example demonstrates how to update the value for an existing key and add a new key-value pair if the key does not exist.

For example,

We start by declaring and initializing a dictionary named my_dict with integer keys and string values.
We update the value for an existing key using key assignment.
We add a new key-value pair using key assignment.
We print the dictionary contents to verify the updates.

Python Program

my_dict = {
    1: 'One',
    2: 'Two',
    3: 'Three'
}

# Update the value for an existing key
my_dict[2] = 'Two Updated'

# Add a new key-value pair
my_dict[4] = 'Four'

# Print the dictionary contents
print('Dictionary contents:')
for key, value in my_dict.items():
    print(f'Key: {key}, Value: {value}')

Output

Dictionary contents:
Key: 1, Value: One
Key: 2, Value: Two Updated
Key: 3, Value: Three
Key: 4, Value: Four

2 Updating the Value for a Key Using the `update` Method

We can update the value for a key in a dictionary in Python using the `update` method. This example demonstrates how to update the value for an existing key and add a new key-value pair using the `update` method.

For example,

We start by declaring and initializing a dictionary named my_dict with integer keys and string values.
We update the value for an existing key using the `update` method.
We add a new key-value pair using the `update` method.
We print the dictionary contents to verify the updates.

Python Program

my_dict = {
    1: 'One',
    2: 'Two',
    3: 'Three'
}

# Update the value for an existing key
my_dict.update({2: 'Two Updated'})

# Add a new key-value pair
my_dict.update({4: 'Four'})

# Print the dictionary contents
print('Dictionary contents:')
for key, value in my_dict.items():
    print(f'Key: {key}, Value: {value}')

Output

Dictionary contents:
Key: 1, Value: One
Key: 2, Value: Two Updated
Key: 3, Value: Three
Key: 4, Value: Four

Summary

In this tutorial, we learned How to Update the Value for a Key in a Dictionary in Python language with well detailed examples.

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How to Update the Value for a Key in a Dictionary in Python