The sorted() method sorts the items of any iterable.
Syntax
sorted(iterable, key, reverse)sorted() Parameters
Python sorted() function parameters:
| Parameter | Condition | Description |
|---|---|---|
iterable |
Required | Any iterable (list, tuple, string, dictionary, set etc.) to sort. |
key |
Optional | A function to specify the sorting criteria. Default value is None. |
reverse |
Optional | Setting it to True sorts the list in reverse order. Default value is False. |
sorted() Return Value
Python sorted() function returns a new sorted list from the items in iterable.
Examples
Example 1: Sort a String
sorted() function sorts strings alphabetically:
my_string = "Tutorial Reference!"
sorted_string = sorted(my_string)
print(sorted_string) # Output: [' ', '!', 'R', 'T', 'a', 'c', 'e', 'e', 'e', 'e', 'f', 'i', 'l', 'n', 'o', 'r', 'r', 't', 'u']output
[' ', '!', 'R', 'T', 'a', 'c', 'e', 'e', 'e', 'e', 'f', 'i', 'l', 'n', 'o', 'r', 'r', 't', 'u']Example 2: Sort a List
sorted() function sorts numbers numerically:
my_list = [123, 99, 23, 25, 1]
x = sorted(my_list)
print(x) # Output: [1, 23, 25, 99, 123]output
[1, 23, 25, 99, 123]Example 3: Sort a Tuple
numbers = (4, 25, 23, 6, 8, 15)
print(sorted(numbers)) # Output: [1, 2, 4, 6, 8, 15]output
[4, 6, 8, 15, 23, 25]Example 4: Sort a Dictionary by Keys
sorted() function sorts a dictionary by keys, by default.
my_dict = {1: 'one', 2: 'two', 3: 'three'}
print(sorted(my_dict)) # Output: [1, 2, 3]output
[1, 2, 3]Example 5: Sort a Dictionary by Values
To sort a dictionary by values use the sorted() function along with
the values() method.
my_dict = {1: 'one', 2: 'two', 3: 'three'}
x = sorted(my_dict.values())
print(x) # Output: ['one', 'three', 'two']output
['one', 'three', 'two']Example 6: Sort in reverse order
You can also sort an iterable in reverse order by setting reverse parameter to True.
numbers = [4, 25, 23, 6, 8, 15]
x = sorted(numbers, reverse=True)
print(x) # Output: [25, 23, 15, 8, 6, 4]output
[25, 23, 15, 8, 6, 4]Example 7: Sort with Key parameter
You can use key parameter for more complex custom sorting. A key parameter specifies a function to be executed on
each list item before making comparisons.
For example, with a list of strings, specifying key=len (the built-in len() function) sorts the strings by length,
from shortest to longest.
my_list = ['orange', 'red', 'green', 'blue']
x = sorted(my_list, key=len)
print(x) # Output: ['red', 'blue', 'green', 'orange']output
['red', 'blue', 'green', 'orange']Example 8: Sort using Custom Function
You can also pass to the sorted() function your own custom function as key function. A key function should take a
single argument and return a key to use for sorting.
For example, sort a list of students (as list of tuple) by age (second element of the tuple):
def sortByAge(e):
return e[1] # return age
students = [('Tom', 30),('Anna', 23), ('Dave', 25)]
x = sorted(students, key=sortByAge)
print(x) # Output: [('Anna', 23), ('Dave', 25), ('Tom', 30)]output
[('Anna', 23), ('Dave', 25), ('Tom', 30)]Example 9: Sort using Lambda
A key function may also be created with the lambda expression. It allows us to in-line function definition.
For example, sort a list of students (as list of tuple) by age (second element of the tuple):
students = [('Tom', 30),('Anna', 23), ('Dave', 25)]
x = sorted(students, key=lambda student: student[1])
print(x) # Output: [('Anna', 23), ('Dave', 25), ('Tom', 30)]output
[('Anna', 23), ('Dave', 25), ('Tom', 30)]Example 10: Sort using Operator Module Functions
To access items of an iterable, Python provides convenience functions
like itemgetter()
and attrgetter()
from operator module.
For example, sort a list of students (as list of tuple) by age (second element of the tuple):
from operator import itemgetter
students = [('Tom', 30),('Anna', 23), ('Dave', 25)]
x = sorted(students, key=itemgetter(1))
print(x) # Output: [('Anna', 23), ('Dave', 25), ('Tom', 30)]output
[('Anna', 23), ('Dave', 25), ('Tom', 30)]Example 11: Multiple Level Sorting (nested sorting)
The operator module functions allow multiple levels of sorting as well.
For example, sort students by grade and then by age:
from operator import itemgetter
students = [('Bob', 'B', 30),
('Anna', 'A', 23),
('Max', 'B', 18),
('Tom', 'A', 29),
('Dave', 'A', 25),
('Ryan', 'B', 15)]
x = sorted(students, key=itemgetter(1,2))
print(x) # [('Anna', 'A', 23), ('Dave', 'A', 25), ('Tom', 'A', 29), ('Ryan', 'B', 15), ('Max', 'B', 18), ('Bob', 'B', 30)]output
[('Anna', 'A', 23), ('Dave', 'A', 25), ('Tom', 'A', 29), ('Ryan', 'B', 15), ('Max', 'B', 18), ('Bob', 'B', 30)]Example 12: Sort Custom Objects
Consider a list of custom objects:
class Student:
def __init__(self, name, grade, age):
self.name = name
self.grade = grade
self.age = age
def __repr__(self):
return repr((self.name, self.grade, self.age))
my_list = [Student('Bob', 'B', 30),
Student('Dave', 'A', 25),
Student('Anna', 'B', 23)]Then, there are different techniques to sort my_list list of custom objects:
result_lambda = sorted(my_list, key=lambda student: student.age)
print(result_lambda) # [('Anna', 'B', 23), ('Dave', 'A', 25), ('Bob', 'B', 30)]output
[('Anna', 'B', 23), ('Dave', 'A', 25), ('Bob', 'B', 30)]from operator import attrgetter
result_attrgetter = sorted(my_list, key=attrgetter('age'))
print(result_attrgetter) # [('Anna', 'B', 23), ('Dave', 'A', 25), ('Bob', 'B', 30)]output
[('Anna', 'B', 23), ('Dave', 'A', 25), ('Bob', 'B', 30)]from operator import attrgetter
result_multi_level = sorted(my_list, key=attrgetter('grade', 'age'))
print(result_multi_level) # [('Dave', 'A', 25), ('Anna', 'B', 23), ('Bob', 'B', 30)]output
[('Dave', 'A', 25), ('Anna', 'B', 23), ('Bob', 'B', 30)]Example 13: Sort a List of Tuples by a Specific Element
For example, let's sort a list of tuples based on the first element of each tuple.
A lambda function is passed as the key argument to sorted() function, specifying that the sorting should be done
based on the first element of each tuple.
my_tuples = [(4, 'banana'), (1, 'apple'), (3, 'cherry'), (2, 'orange')]
sorted_tuples = sorted(my_tuples, key=lambda x: x[0])
print(sorted_tuples) # Output: [(1, 'apple'), (2, 'orange'), (3, 'cherry'), (4, 'banana')]output
[(1, 'apple'), (2, 'orange'), (3, 'cherry'), (4, 'banana')]Example 14: Sort a List of Dictionaries by a Specific Key
For example, let's sort a list of dictionaries based on the value of a specific key. In this case we sort based on
the age key of each dictionary.
my_dicts = [{'name': 'Tom', 'age': 26}, {'name': 'Dave', 'age': 25}, {'name': 'Anna', 'age': 23}]
sorted_dicts = sorted(my_dicts, key=lambda x: x['age'])
print(sorted_dicts) # Output: [{'name': 'Anna', 'age': 23}, {'name': 'Dave', 'age': 25}, {'name': 'Tom', 'age': 26}]output
[{'name': 'Anna', 'age': 23}, {'name': 'Dave', 'age': 25}, {'name': 'Tom', 'age': 26}]