Returns a casefolded string
casefold() method returns a casefolded (lowercase but more aggressive) copy of the string.
The method does not change the original string.
Casefolded strings are usually used to ‘normalize‘ text for the purposes of caseless comparison (especially when you want to take characters of many different languages into account).
Example: Make a string casefolded
S = 'Hello, World!' x = S.casefold() print(x) # hello, world!
casefold() vs lower()
Casefolding is similar to lowercasing but more aggressive because it is intended to remove all case distinctions in a string.
For example, the German lowercase letter ‘ß‘ is equivalent to ‘ss‘. Since it is already lowercase, lower() would do nothing to ‘ß‘, but
casefold() converts it to ‘ss‘.
S = 'Das straße' x = S.casefold() print(x) # das strasse
S = 'Das straße' x = S.lower() print(x) # das straße
If you are working strictly in the English language,
casefold() returns exactly the same results.
However, if you are trying to normalize text from other languages that use more than English 26-letter alphabet, use
casefold() to compare your strings for more consistent results.