Understanding sorted() with ord() and lambda in Python for Custom Sorting

Dive deep into how to use `sorted()` in Python along with `ord()` and `lambda` for custom string sorting based on specific rules.
---

Visit these links for original content and any more details, such as alternate solutions, latest updates/developments on topic, comments, revision history etc. For example, the original title of the Question was: Usage of sorted with ord() and lambda in python

If anything seems off to you, please feel free to write me at vlogize [AT] gmail [DOT] com.
---
Understanding sorted() with ord() and lambda in Python for Custom Sorting

Sorting strings in Python can be a simple task when it comes to alphabetical order. However, when specific sorting criteria need to be applied, it can become quite challenging. In this post, we will discuss how to use sorted() along with ord() and lambda functions to create a custom sorting mechanism based on specified rules.

The Problem: Custom Sorting Rules

Let's look at the problem statement: We have an alphanumeric string, and we want to sort it according to the following rules:

All lowercase letters should appear before uppercase letters.

All uppercase letters should appear before digits.

Odd digits should appear before even digits.

Given a string, you might want a way to achieve this sorting. The solution proposed in an exercise on Hackerrank is quite efficient and can provide a one-liner solution.

The Solution Approach

The solution provided is as follows:

[[See Video to Reveal this Text or Code Snippet]]

Let's break this down step by step.

Understanding Each Component

sorted() Function: This function takes an iterable and sorts it based on the provided key.

ord() Function: This function returns the Unicode code point (essentially the ASCII value) of a character.

lambda Function: It's a small anonymous function in Python, used here to specify custom sort criteria.

How the Sorting Works

Now, let's analyze the sorting criteria encapsulated in the lambda function:

[[See Video to Reveal this Text or Code Snippet]]

Breaking it Down:

-ord(c) >> 5:

This extracts the column index from the ASCII table of the character.

Right shifting by 5 (>> 5) divides the ord(c) value by 32, effectively giving us a value corresponding to the character type (0 for digits, 1 for uppercase, 2 for lowercase).

The negative sign is introduced to ensure that lowercase letters (the largest values in the sort) are prioritized by reversing the order.

c in '02468':

This evaluates to True for even digits and False for odd ones.

Placing this next in the sort criteria ensures that odd digits come before even digits.

c:

Finally, sorting by the character itself ensures that if two characters share the same sort precedence, they will be sorted lexicographically.

A Deeper Insight: Why Use Right Shift?

You may wonder, why do we use the right shift operator (>>) in the sorting process? The ASCII table can be segmented into columns where:

Column 1 consists of digits,

Column 2 has uppercase letters,

Column 3 encloses lowercase letters.

Using right shift effectively reduces the complexity by grouping characters into these categories. This allows the sort criteria to be simpler and more efficient.

Final Working Example

Let’s see the final result in action:

[[See Video to Reveal this Text or Code Snippet]]

The expected output for the input Sorting1234 will be ginoS1324.

Conclusion

The combination of sorted(), ord(), and lambda in Python is a powerful way to achieve customized sorting strategies to meet any requirements. By understanding the principles behind how these functions interact, you can effectively manipulate strings to fit various sorting criteria.

Now that you’ve seen how to implement a complex sorting mechanism, you can experiment with different rules and input to see how flexible this approach can be!

If you have any further questions or need examples, feel free to leave a comment below!