The dictionary is a built-in data type in Python, serving as a collection of key-value pairs. Unlike lists or tuples, dictionaries are mutable, allowing for modifications. However, dictionary keys are immutable and must maintain uniqueness within the dictionary. Although there isn’t a dedicated “add” method, multiple approaches exist for incorporating new elements or modifying existing ones in a dictionary. This article explores techniques like the assignment operator, the update() method, and the merging and updating dictionary operators, which enable adding and modifying entries within Python dictionaries.<\/p>\n
Adding to a Dictionary Using the = Assignment Operator<\/p>\n
Example:<\/b><\/p>\n Output:<\/b><\/p>\n In this example, the key ‘c’ is appended to the dictionary my_dict with the corresponding value 3 using the = assignment operator. The resulting dictionary will include the new key-value pair: {‘a’: 1, ‘b’: 2, ‘c’: 3}.<\/p>\n If a key already exists in the dictionary, using the assignment operator updates or overwrites the value.<\/p>\n The following example illustrates how to create a new dictionary and subsequently utilize the assignment operator (=) to update values and add key-value pairs:<\/p>\n Example:<\/b><\/p>\n Output:<\/b><\/p>\n The output reveals that the new value overwrites the value of ‘a’, the value of ‘b’ remains unchanged, and new key-value pairs are introduced for ‘c’ and ‘d’.<\/p>\n Using the = assignment operator replaces existing fundamental values with new ones. If you know your program could contain duplicate keys and wish to avoid overwriting the original values, you can selectively add values using an if statement.<\/p>\n Continuing with the example from the preceding section, you can use if statements to add only new key-value pairs to the dictionary:<\/p>\n\r\nmy_dict = {'a': 1, 'b': 2}\r\nmy_dict['c'] = 3\r\nprint(my_dict)\r\n<\/code><\/pre>\n\u00a0{'a': 1, 'b': 2, 'c': 3}<\/code><\/pre>\ndict_example = {'a': 1, 'b': 2}\r\nprint(\"original dictionary: \", dict_example)\r\ndict_example['a'] = 100\u00a0 # existing key, overwrite\r\ndict_example['c'] = 3\u00a0 # new key, add\r\ndict_example['d'] = 4\u00a0 # new key, add\u00a0\r\nprint(\"updated dictionary: \", dict_example)<\/code><\/pre>\noriginal dictionary:\u00a0 {'a': 1, 'b': 2}\r\nupdated dictionary:\u00a0 {'a': 100, 'b': 2, 'c': 3, 'd': 4}<\/code><\/pre>\nAdding to a Dictionary Without Overwriting Values:<\/h3>\n
dict_example = {'a': 1, 'b': 2}\r\nprint(\"original dictionary: \", dict_example)\r\ndict_example['a'] = 100\u00a0 # existing key, overwrite\r\ndict_example['c'] = 3\u00a0 # new key, add\r\ndict_example['d'] = 4\u00a0 # new key, add\u00a0\r\nprint(\"updated dictionary: \", dict_example)\r\n# add the following if statements\r\nif 'c' not in dict_example.keys():\r\n\u00a0 \u00a0 dict_example['c'] = 300\r\nif 'e' not in dict_example.keys():\r\n\u00a0 \u00a0 dict_example['e'] = 5\r\nprint(\"conditionally updated dictionary: \", dict_example)<\/code><\/pre>\n