如何填充字典python中的空值？

my_dict = {'key1': '', 'key2': 'value2', 'key3': '', 'key4': 'value4'}
for key in my_dict:
    if my_dict[key] == '':
        my_dict[key] = 'default value'

my_dict = {'key1': '', 'key2': 'value2', 'key3': '', 'key4': 'value4'}
my_dict = {key: 'default value' if value == '' else value for key, value in my_dict.items()}

my_dict = {'key1': '', 'key2': 'value2', 'key3': '', 'key4': 'value4'}
for key in my_dict:
    my_dict.setdefault(key, 'default value')

from collections import defaultdict

my_dict = {'key1': '', 'key2': 'value2', 'key3': '', 'key4': 'value4'}
my_dict = defaultdict(lambda: 'default value', {key: value for key, value in my_dict.items()})