str.isupper() All uppercase
Last updated: 2026-09-22
str.isupper() All uppercase
str.isupper() returns True if there is at least one uppercase letter and no lowercase letters.
| Category | String Methods |
|---|---|
| Kind | Built-in Type Method |
| Python Version | all |
📝 Syntax
str.isupper()Returns：bool. True if it has at least one uppercase letter and no lowercase ones.
Mutates the original：No (returns a new object)
▶ Example
Edit the code, press Run, and see the result in the output panel:
Output：
True
False💡 Related Cases
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❓ FAQ
QWhat does '123'.isupper() return?
AFalse. isupper() requires at least one uppercase letter, so pure digits return False.
QWhat about a string with mixed case?
A'Hello'.isupper() is False. 'HELLO!'.isupper() is True, because punctuation does not affect the result.
QWhen do isupper() and islower() both return False?
AFor strings such as pure digits or pure symbols that contain no letters, both return False. isupper() and islower() are mutually exclusive but not complementary.
