How to Set a Default Value for a Key in a Dictionary in Python

How to Set a Default Value for a Key in a Dictionary in Python ?

Answer

To set a default value for a key in a dictionary in Python, you can use the `setdefault` method or the `defaultdict` class from the `collections` module.

✐ Examples

1 Setting a Default Value for a Key Using `setdefault` Method

We can set a default value for a key in a dictionary in Python using the `setdefault` method. This example demonstrates how to use the `setdefault` method to set a default value if the key does not exist.

For example,

We start by declaring and initializing an empty dictionary named my_dict.
We use the `setdefault` method to set a default value for a key if it does not exist.
We print the dictionary contents to verify the key-value pairs.

Python Program

my_dict = {}

# Set default value for a key
key_to_check = 1
my_dict.setdefault(key_to_check, 'Default')

# 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: Default

2 Setting Default Values Using `defaultdict`

We can use the `defaultdict` class from the `collections` module to set default values for keys in a dictionary in Python. This example demonstrates how to use `defaultdict` to set default values for keys.

For example,

We start by importing the `defaultdict` class from the `collections` module.
We declare and initialize a `defaultdict` named my_dict with a default value of type string.
We access keys to see the default values being set.
We print the dictionary contents to verify the key-value pairs.

Python Program

from collections import defaultdict

# Declare and initialize a defaultdict
my_dict = defaultdict(lambda: 'Default')

# Access keys to see default values being set
my_dict[1]
my_dict[2]

# 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: Default
Key: 2, Value: Default

Summary

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

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How to Set a Default Value for a Key in a Dictionary in Python