str.islower() All lowercase
Last updated: 2026-09-22
str.islower() All lowercase
str.islower() returns True if there is at least one lowercase letter and no uppercase letters.
| Category | String Methods |
|---|---|
| Kind | Built-in Type Method |
| Python Version | all |
📝 Syntax
str.islower()Returns：bool. True if it has at least one lowercase letter and no uppercase 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'.islower() return?
AFalse. islower() requires at least one lowercase letter; pure digits contain no letters, so it returns False.
QWhat happens when there is one uppercase letter?
AIt returns False. 'hello!'.islower() is True but 'Hello'.islower() is False.
QWhat about Chinese?
AChinese has no case distinction, so '你好'.islower() returns False (it contains no cased letters).
