str.casefold() Aggressive lowercase
Last updated: 2026-09-22
str.casefold() Aggressive lowercase
str.casefold() returns a lowercased string optimized for caseless matching (e.g., German ß).
| Category | String Methods |
|---|---|
| Kind | Built-in Type Method |
| Python Version | all |
📝 Syntax
str.casefold()Returns：str. A lowercased copy optimized for caseless comparisons.
Mutates the original：No (returns a new object)
▶ Example
Edit the code, press Run, and see the result in the output panel:
Output：
strasse
True💡 Related Cases
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❓ FAQ
QWhat is the difference between casefold() and lower()?
Acasefold() is more aggressive than lower(): it can fold special characters such as the German ß into 'ss', which lower() does not. Use casefold() for case-insensitive comparisons.
QWhat is the recommended way to compare two strings ignoring case?
AUse s1.casefold() == s2.casefold(). For example, 'Straße'.casefold() == 'STRASSE'.casefold() is True, while comparing with lower() gives False.
QDoes casefold() modify the original string?
ANo. It returns a new folded string and leaves the original unchanged.
