Python String lower() Method

Syntax

The Syntax of the str.lower() function is:

str.lower()

Here, str is a string.

Parameters

The str.lower() function does not take any parameters.

Return Value

The str.lower() function returns the copy of a lowercase string. It converts all the uppercase characters into lowercase, and if the string does not contain uppercase characters, it returns the original string as-is.

Example 1: Python Program to convert string from uppercase to lowercase

# Text with Mixed Case
text = "PYTHON is both Compiled as well as an Interpreted Language"
print(text.lower())

# Alphanumeric with special characters Text
text = "There are 7 DAYS in a WEEK !!!"
print(text.lower())

Output

python is both compiled as well as an interpreted language
there are 7 days in a week !!!

Example 2: Convert all the elements in the list to lowercase

The Program iterates all the elements in the list and prints them in lowercase.

programming_languages = ["PYTHON","C#","GO","JAVA","JAVASCRIPT"]

for ele in programming_languages:
    print(ele.lower())

Output

python
c#
go
java
javascript

Example 3: How lower() method is used in the Program

Let's say if you have an application that stores the username in lowercase and if the user enters their username in uppercase or title case, you first convert them into lowercase using the lower() method and check if it exists in the Database.

username_list = ["admin", "user1", "jack", "w3basic"]

user = input("Enter your username:")
if user.lower() in username_list:
    print("Username Found")
else:
    print("Invalid Username")

Output

Enter your username:ADMIN
Username Found

Enter your username:Administrator
Invalid Username

Reference: Python Official Docs