Python String upper() Method

The Python string upper() method returns a new string with lowercase letters changed to uppercase.

This page explains what upper() does, how to use it, what it returns, and a few common beginner mistakes. It stays focused on the method itself.

Quick example

text = "Hello World"
result = text.upper()
print(result)
# HELLO WORLD

upper() returns a new string with letters changed to uppercase. It does not change the original string in place.

What upper() does

  • upper() returns a copy of a string with lowercase letters converted to uppercase
  • It works on string values only
  • It returns a new string
  • The original string stays unchanged

If you are new to strings, see what a string is in Python or Python strings explained: basics and examples.

Basic syntax

The syntax is:

string.upper()

Important points:

  • It takes no arguments
  • You call it on a string variable or string literal
  • It returns the uppercase version of the string

Example with a variable:

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

Example with a string literal:

print("hello".upper())

Simple example

Here is a basic example that converts a lowercase word to uppercase and stores the result in a new variable:

word = "banana"
uppercase_word = word.upper()

print(word)
print(uppercase_word)

Output:

banana
BANANA

What this shows:

  • word keeps its original value
  • uppercase_word stores the returned value from upper()

upper() does not change the original string

Strings are immutable in Python. That means you cannot change the characters inside a string directly.

So this method:

name = "alice"
name.upper()

print(name)

Output:

alice

Even though upper() was called, name did not change because the result was not saved.

If you want to keep the uppercase version, assign it back to the variable:

name = "alice"
name = name.upper()

print(name)

Output:

ALICE

This is one of the most common beginner mistakes with string methods.

What happens to numbers, spaces, and symbols

upper() only changes letters that have uppercase forms.

  • Numbers stay the same
  • Spaces stay the same
  • Punctuation stays the same
  • Only letters are changed

Example:

text = "Room 7, table #3!"
print(text.upper())

Output:

ROOM 7, TABLE #3!

The letters changed to uppercase, but the number, space, comma, and symbol stayed the same.

When to use upper()

upper() is useful when you want to standardize text.

Common uses:

  • Standardize user input for comparisons
  • Format labels or headings
  • Make text easier to compare in simple cases

Example: simple comparison

answer = "yes"

if answer.upper() == "YES":
    print("Matched")

Output:

Matched

This can help when users type different letter cases, such as yes, Yes, or YES.

Common mistakes

Forgetting to save the returned value

A very common mistake is expecting text.upper() to change the original variable automatically.

Wrong:

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

Output:

hello

Correct:

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

Output:

HELLO

Trying to call upper() on a non-string value

upper() is a string method. If the value is not a string, it will fail.

Example:

number = 123
print(number.upper())

This causes an error because int objects do not have an upper() method.

If needed, convert the value to a string first:

number = 123
print(str(number).upper())

Output:

123

Confusing upper() with title case

upper() makes all letters uppercase. It does not make every word start with a capital letter.

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

Output:

HELLO WORLD

If your goal is different, another method may fit better. For example, lower() makes text lowercase, and replace() changes parts of a string.

Related string methods

These string methods are often used with upper():

  • lower() for lowercase text
  • strip() for removing leading and trailing whitespace
  • replace() for changing parts of a string
  • startswith() and endswith() for checks

Example:

text = "  hello world  "

cleaned = text.strip()
loud = cleaned.upper()

print(loud)

Output:

HELLO WORLD

FAQ

Does upper() change the original string?

No. It returns a new uppercase string. Save the result if you want to keep it.

Does upper() take any arguments?

No. The method is called with empty parentheses: text.upper().

What happens to numbers and symbols?

They stay the same. upper() only changes letters that can be converted to uppercase.

Can I use upper() for case-insensitive comparison?

Yes, for simple cases. Convert both strings before comparing them.

Example:

a = "python"
b = "PYTHON"

print(a.upper() == b.upper())

Output:

True

See also