Python String islower()

Summary: in this tutorial, you’ll learn how to use the Python string islower() method to check if all cases characters are lowercase.

Introduction to the Python String islower() method #

The following shows the syntax of the string islower() method:

str.islower()Code language: CSS (css)

The string islower() method returns True if all cased characters are lowercase. Otherwise, it returns False.

If the string doesn’t contain any cased characters, the islower() method also returns False.

In Python, cased characters are the ones with general category property being one of:

• Lu (letter, uppercase)
• Ll (letter, lowercase)
• Lt (letter, titlecase)

Note that to return a copy of the string with all characters converted to lowercase, you use the string lower() method.

Python String islower() method examples #

Let’s take some examples of using the string islower() method.

The following example uses the islower() to check if all characters of an email are lowercase:

email = '[email protected]'
is_lowercase = email.islower()
print(is_lowercase)Code language: PHP (php)

Output:

TrueCode language: PHP (php)

However, the following example returns False because the first character of the string is uppercase:

email = '[email protected]'
is_lowercase = email.islower()
print(is_lowercase)Code language: PHP (php)

Output:

FalseCode language: PHP (php)

The following example return False because the string has no cased characters:

number_str = '123'
is_lowercase = number_str.islower()
print(is_lowercase)Code language: PHP (php)

Output:

FalseCode language: PHP (php)

Summary #

• Use the Python string islower() method to determine if all cased characters of a string are lowercase.