How to Sort a Dictionary by Key in Python

Sorting a dictionary by its keys in Python can be achieved using the built-in sorted() function. Here are two possible approaches to accomplish this:

Approach 1: Using the sorted() function

The sorted() function takes an iterable (such as a dictionary) and returns a new sorted list based on the elements in the iterable. To sort a dictionary by its keys, we can pass the dictionary’s keys() method as the argument to the sorted() function.

Here’s an example:

my_dict = {'c': 3, 'a': 1, 'b': 2}
sorted_dict = {k: my_dict[k] for k in sorted(my_dict.keys())}
print(sorted_dict)

Output:

{'a': 1, 'b': 2, 'c': 3}

In the example above, the sorted() function is applied to the keys of the my_dict dictionary. The keys are then used to construct a new dictionary sorted_dict with the same key-value pairs as the original dictionary, but sorted by the keys.

Approach 2: Using the sorted() function with lambda

Another way to sort a dictionary by its keys is to use a lambda function as the key parameter to the sorted() function. This lambda function specifies that the keys should be used for sorting.

Here’s an example:

my_dict = {'c': 3, 'a': 1, 'b': 2}
sorted_dict = {k: my_dict[k] for k in sorted(my_dict.keys(), key=lambda x: x)}
print(sorted_dict)

Output:

{'a': 1, 'b': 2, 'c': 3}

In the above example, the lambda function key=lambda x: x is used to specify that the keys themselves should be used for sorting. This lambda function returns the keys as-is, resulting in the dictionary being sorted by its keys.

Best Practices

When sorting a dictionary by its keys, it’s important to note that dictionaries in Python are inherently unordered. The order of the keys in a dictionary is not guaranteed to be the same as the order in which they were inserted. Therefore, if you need to maintain a specific order for your dictionary, you should consider using an ordered dictionary, such as the collections.OrderedDict class.

Here’s an example of how to use collections.OrderedDict to sort a dictionary by its keys:

from collections import OrderedDict

my_dict = {'c': 3, 'a': 1, 'b': 2}
sorted_dict = OrderedDict(sorted(my_dict.items(), key=lambda x: x[0]))
print(sorted_dict)

Output:

OrderedDict([('a', 1), ('b', 2), ('c', 3)])

In the above example, the sorted() function is used to sort the items of the dictionary my_dict based on their keys. The key parameter is set to lambda x: x[0], which specifies that the first element of each item (i.e., the key) should be used for sorting. The sorted items are then used to create a new OrderedDict object sorted_dict, which maintains the order of the keys.