Python String upper() Method

The upper() method in Python converts all lowercase characters in a string to uppercase. It is a built-in string method and is very useful when you want to standardize or compare text.

Syntax

string.upper()

Parameters:

• This method takes no parameters.

Returns:

• A new string with all characters in uppercase.

Example 1: Basic Usage

text = "hello world"
print(text.upper())

HELLO WORLD

Example 2: Mixed Case String

name = "Alice123"
print(name.upper())

ALICE123

Note: Numbers and symbols remain unchanged.

Use Cases

• To standardize user input (e.g., emails, usernames)
• For case-insensitive string comparisons
• To make output visually distinct (e.g., titles, warnings)

Does it change the original string?

No. Strings in Python are immutable. upper() returns a new string — it does not modify the original.

word = "python"
new_word = word.upper()
print(word)      # python
print(new_word)  # PYTHON

Common Mistakes

• Trying to use upper without parentheses – remember it’s a method: string.upper()
• Assuming it changes the original string – you must assign the result if needed

Interview Tip

In coding tests, upper() is handy for making string comparisons or normalizing data without worrying about the input case.

Summary

• upper() converts all characters in a string to uppercase.
• Does not affect numbers or special characters.
• Returns a new string – original remains unchanged.

Practice Problem

Write a program that asks the user to enter their name and prints it in all capital letters.

name = input("Enter your name: ")
print("Your name in uppercase is:", name.upper())