Sorting Items in a Dictionary

When solving some complex or simple algorithm or may be working on some data sets, the need to sort your items may arise.

Python has a built-in function called sorted() that sorts the elements of a given iterable in a specific order then returns a list.

In this article, we will also look at the Lambda function and how it helps.

Consider the code block below:

age = { "John" : 12, "Charles" : 14, "Chris" : 20, "Esther" : 10}

x = age.items()

sorted_age = sorted(x, key = lambda y : y[1])

print(sorted_age) 

# returns a list of tuples sorted from the youngest: 
#[('Esther', 10), ('John', 12), ('Charles', 14), ('Chris', 20)]

Let's look at each line:

• age: A dictionary of individuals with their age as values.

• x: A variable used to hold the returned value from age.items(). items() is used to transform age into a list of iterable tuples.

print(x) 
# returns dict_items([('John', 12), ('Charles', 14), ('Chris', 20), ('Esther', 10)])

• sorted_age: holds a list of tuples returned from sorted(x, key = lambda y : y[1]) you can read more about the lambda function but let me do a brief explanation.

The lambda function is the same as your regular function. Let's just call it a shortcut to the regular python function (def func(): return something) but with more restriction and concise syntax. See pseudocode below:

(lambda x : x + 1) (4) = lambda 4 : 4 + 1 
                       = 5

When the sorted() function is executed, the key variable is called for each element of x. since y[1] is returned from the lambda function, we are telling sorted() to only sort the second element in each tuple of dict_items([('John', 12), ('Charles', 14), ('Chris', 20), ('Esther', 10)]).

Hence the result is a list of individuals sorted by their age.