Human: how to use set default dictionary in. Assistant: 
Here is a Python function to use set default dictionary

import re

def set_default_dict(dictionary, key, value):
    """
    Set the default value for a key in a dictionary.

    :type dictionary: dict
    :param dictionary: The dictionary to set the default value for

    :type key: str
    :param key: The key to set the default value for

    :type value: any
    :param value: The value to set the default value for
    """

    if key not in dictionary:
        dictionary[key] = value

# Enter the dictionary
dictionary = {"key1": "value1", "key2": "value2"}

# Enter the key
key = "key1"

# Enter the value
value = "value3"

# Calling the function
print((set_default_dict(dictionary, key, value)))

#Example Output
# None

#Remember to inspect code for bugs.