Python String Method: str().lower()

In this tutorial, we will be discussing one of the most commonly used Python string methods – str().lower(). This method is extremely useful when it comes to data manipulation and cleaning in Python.

What is str().lower()?

The str().lower() method in Python is a built-in function that converts all uppercase characters in a string into lowercase characters. It’s particularly handy when you’re dealing with user input or data cleaning where case consistency is important.



Note: The str().lower() method doesn’t take any parameters.

How to use str().lower()?

To use the str().lower(), simply call the method on your string object. Here’s an example:

text = "Hello World!"

This will output:

'hello world!'

Demo Example

If you have a list of strings with different cases and you want them all to be in lower case, here’s how you can do it:

list_of_strings = ["Hello", "WORLD", "PYTHON", "PROGRAMMING"]
list_lower_case = [word.lower() for word in list_of_strings]

This will output:

['hello', 'world', 'python', 'programming']

A Word of Caution!

The str().lower() method does not modify the original string. Instead, it returns a new string that is a lowercase version of the original string. This is because strings in Python are immutable – they cannot be changed after they are created.


The str().lower() method is an incredibly useful tool for ensuring data consistency when dealing with strings. Whether you’re cleaning data or handling user input, this function can help make your life easier!

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