String Case Methods in Python

Overview

This lecture explains various string methods in Python used to change the case of text and check for case formatting.

The upper() Method

• The upper() method converts all letters in a string to uppercase.
• Syntax: string.upper()
• Example: "hello I am just preet".upper() results in "HELLO I AM JUST PREET".
• Method does not take any arguments; parentheses are required.

The lower() Method

• The lower() method converts all letters in a string to lowercase.
• Syntax: string.lower()
• Example: "Hello I am just preet".lower() results in "hello i am just preet".

The capitalize() Method

• The capitalize() method returns a string with the first character uppercase and the rest lowercase.
• Syntax: string.capitalize()
• Example: "maruti Suzuki".capitalize() results in "Maruti suzuki".
• If the first character is not a letter (e.g., a digit), the string remains unchanged.

The isupper() Method

• The isupper() method returns True if all letters in the string are uppercase; otherwise, it returns False.
• Syntax: string.isupper()
• Example: "HELLO".isupper() returns True; "Hello friends".isupper() returns False.
• This method returns a Boolean value, unlike upper() which returns a string.

The islower() Method

• The islower() method returns True if all letters in the string are lowercase; otherwise, it returns False.
• Syntax: string.islower()
• Example: "hello".islower() returns True; "HELLO FRIENDS".islower() returns False.
• This is the opposite of the isupper() method.

Key Terms & Definitions

• Uppercase — Letters in capital form (A, B, C...).
• Lowercase — Letters in small form (a, b, c...).
• Boolean value — Data type with only two values: True or False.
• String method — A function that can be used on a string object.

Action Items / Next Steps

• Practice using each method (upper(), lower(), capitalize(), isupper(), islower()) in the Python interpreter.
• Experiment with sample strings to observe each method's effect.