**Summary:** This blog explores the steps to sort elements of a **Set**.

Python offers the built-in `sorted()`

function to sort elements in container objects such as a set or a list. For example: `sorted({1, 5, 2})`

sorts the elements in the set and returns the sorted list `[1, 2, 5]`

.

**Note**: All the solutions provided below have been verified using Python 3.9.0b5

Table of Contents

## Problem Formulation

Imagine that one has the following **Set** in Python.

set(['4.928857000', '0.030778000', '4.927327899', '0.002949589', '0.023685000', '11.463524000', '0.0270662958'])

## Desired Output:

How does one sort this **Set**, so that the output is the following List.

['0.002949589', '0.023685000', '0.0270662958', '0.030778000', '4.927327899', '4.928857000', '11.463524000']

## Background

Wikipedia: “In computer science, a **Set** is an abstract data type that can store unique values, without any particular order.”

Python defines a **Set** as an unordered collection with no duplicate elements. In Python, a **Set** is a built-in data-type that stores collections of data. Think of a **Set** as container type, similar to lists, tuples and dictionaries. Python programmers use sets to test for membership and to remove duplicate items.

## How to Sort a Set?

Since 2013, the **Python Community** has asked the question about sorting a **Set**, about 260k times. That is incredible, given the above background of a **Set**.

So first things first! In Python, Elements in a given **Set**, do not have any specific order. One can iterate thru each element in a **Set** and sort the resulting output. Python offers the built-in **sorted()** function to sort elements in container objects such as a **Set** or a **List**. The following code examples show how to use the `sorted()`

function.

$ python Python 3.9.0b5 (default, Oct 19 2020, 11:11:59) >>> >>> ## This is the original Set Object whose elements will be sorted. >>> my_set = set(['4.928857000', '0.030778000', '4.927327899', '0.002949589', '0.023685000', '11.463524000', '0.0270662958']) >>> >>> ## This is the type of my_set. Yes, Python confirms, it is a set!! >>> type(my_set) <class 'set'> >>> >>> ## The Python Built-in function “sorted()” iterates thru the elements in the >>> ## given set argument and sorts them. >>> my_sorted_elements = sorted(my_set) >>> >>> ## By default, the sorted() function assumes the following… >>> ## The elements are strings >>> ## The sorting is done in ascending order. >>> my_sorted_elements ['0.002949589', '0.023685000', '0.0270662958', '0.030778000', '11.463524000', '4.927327899', '4.928857000'] >>> >>> ## The sorted() function sorts the elements and returns a list object. >>> type(my_sorted_elements) <class 'list'> >>>

The astute reader may have noticed above, that the sorting order is funky. That is: ‘0.030778000’, ‘11.463524000’, ‘4.927327899’

This is because the ** sorted()** function assumes the

**set**elements are

**strings,**by default. Consider the first element in the

`my_sorted_elements`

list.>>> my_sorted_elements[0] '0.002949589' >>> >>> type(my_sorted_elements[0]) <class 'str'> >>>

## How to Sort Elements As Floats?

It is important to note that the sorted elements in the returned list are still **strings**. The **sorted()** function converts the elements into **floats**. It does this for the sole purpose of sorting them. After it sorts the elements, the **sorted()** function reverts them back to be **string** elements. The following code example shows how to sort the **Set** elements as **floats**.

$ python Python 3.9.0b5 (default, Oct 19 2020, 11:11:59) >>> >>> ## This is the original Set Object whose elements will be sorted. >>> my_set = set(['4.928857000', '0.030778000', '4.927327899', '0.002949589', '0.023685000', '11.463524000', '0.0270662958']) >>> >>> ## The Python Built-in function “sorted()” iterates thru the elements in the >>> ## given my_set argument and sorts them. This time as floats. >>> my_sorted_elements = sorted(my_set, key=float) >>> >>> ## It should be noted that the elements in the returned list are still strings. >>> ## The sorted() function converts the elements into floats, for the sole purpose >>> ## of sorting them, then reverts them back to be string elements >>> my_sorted_elements ['0.002949589', '0.023685000', '0.0270662958', '0.030778000', '4.927327899', '4.928857000', '11.463524000'] >>> >>> my_sorted_elements[0] '0.002949589' >>> type(my_sorted_elements[0]) <class 'str'> >>> >>> ## my_sorted_elements continues to be a list object. >>> type(my_sorted_elements) <class 'list'> >>>

## Can The Sorting Order Be Changed?

The `sorted()`

built-in function also offers the **‘reverse’** argument, to change the sorting order. Setting **reverse=True**, changes the sorting order to be descending. The following code shows how to change the sorting order to descending.

$ python Python 3.9.0b5 (default, Oct 19 2020, 11:11:59) >>> >>> ## This is the original Set Object whose elements will be sorted. >>> my_set = set(['4.928857000', '0.030778000', '4.927327899', '0.002949589', '0.023685000', '11.463524000', '0.0270662958']) >>> >>> ## As before, the Python Built-in “sorted()” function iterates thru the elements in the >>> ## given my_set argument and sorts them as floats. This is now in done in descending >>> ## order, because of the ‘reverse’ argument. >>> my_sorted_elements = sorted(my_set, key=float, reverse=True) >>> >>> ## Also as before, the elements in the returned list are still strings. >>> ## Also as before, the sorted() function converts the elements into floats, for the >>> ## sole purpose of sorting them, then reverts them back to be string elements >>> my_sorted_elements ['11.463524000', '4.928857000', '4.927327899', '0.030778000', '0.0270662958', '0.023685000', '0.002949589'] >>> >>> my_sorted_elements[0] '11.463524000' >>> type(my_sorted_elements[0]) <class 'str'> >>> >>> ## Again as before, my_sorted_elements continues to be a list object. >>> type(my_sorted_elements) <class 'list'> >>>

## What Happens If The Original Set Elements Are Floats?

The process remains the same if the original **Set** elements are **floats**. One does not need to provide the **‘key’** argument. Python is smart enough to recognize the elements as **floats**. Consider the following code.

$ python Python 3.9.0b5 (default, Oct 19 2020, 11:11:59) >>> >>> ## This is the original Set Object whose elements will be sorted. This time the elements >>> ## are floats. >>> my_set = set([4.928857000, 0.030778000, 4.927327899, 0.002949589, 0.023685000, 11.463524000, 0.0270662958]) >>> >>> type(my_set) <class 'set'> >>> ## Note that the ‘key’ argument is not needed, to sort as floats. >>> my_sorted_elements = sorted(my_set) >>> >>> ## Python recognizes the set elements as floats and sorts them in ascending order >>> my_sorted_elements [0.002949589, 0.023685, 0.0270662958, 0.030778, 4.927327899, 4.928857, 11.463524] >>> >>> ## As before, my_sorted_elements continues to be a list object. >>> type(my_sorted_elements) <class 'list'> >>> >>> ## Unlike the earlier sections, the elements in the my_sorted_elements list are >>> ## actually floats. >>> my_sorted_elements[0] 0.002949589 >>> type(my_sorted_elements[0]) <class 'float'> >>>

## What About Sorting In Descending Order?

Python is a very intuitive scripting language. If there is sorting in ascending order, one can be sure there is a way to sort in descending order too. The **‘reverse’** argument tells the **sorted()** function to sort in descending order. Consider the following code.

$ python Python 3.9.0b5 (default, Oct 19 2020, 11:11:59) >>> >>> ## This is the original Set Object whose elements will be sorted. As above, the >>> ## elements are float values. >>> my_set = set([4.928857000, 0.030778000, 4.927327899, 0.002949589, 0.023685000, 11.463524000, 0.0270662958]) >>> >>> type(my_set) <class 'set'> >>> ## Note that the ‘key’ argument is not needed, to sort as floats. >>> my_sorted_elements = sorted(my_set, reverse=True) >>> >>> ## Python recognizes the set elements as floats and sorts them in ascending order >>> my_sorted_elements [11.463524, 4.928857, 4.927327899, 0.030778, 0.0270662958, 0.023685, 0.002949589] >>> >>> ## As before, my_sorted_elements continues to be a list object. >>> type(my_sorted_elements) <class 'list'> >>> >>> ## Unlike the earlier sections, the elements in the my_sorted_elements list are >>> ## actually floats. >>> my_sorted_elements[0] 11.463524 >>> type(my_sorted_elements[0]) <class 'float'> >>>

## Conclusion

In Python, the **Set** object contains unordered elements. But, one can use the **sorted()** built-in function to sort its elements. The original **Set** itself remains unchanged. The **sorted()** function returns a **List** object with the sorted elements. The **sorted()** function can take various arguments. These arguments specify the type of elements and/or the sorting order.

## Finxter Academy

This blog was brought to you by **Girish Rao**, a student of Finxter Academy. You can find his Upwork profile here.

## Reference

All research for this blog article was done using Python Documents, the Google Search Engine and the shared knowledge-base of the Finxter Academy and the Stack Overflow Communities.