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Python String upper() Method – Convert to Uppercase


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())


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