{"id":1968,"date":"2020-12-28T04:35:37","date_gmt":"2020-12-28T04:35:37","guid":{"rendered":"https:\/\/www.pythontutorial.net\/?page_id=1968"},"modified":"2020-12-28T04:36:15","modified_gmt":"2020-12-28T04:36:15","slug":"python-string-casefold","status":"publish","type":"page","link":"https:\/\/www.pythontutorial.net\/python-string-methods\/python-string-casefold\/","title":{"rendered":"Python String casefold()"},"content":{"rendered":"\n

Summary<\/strong>: in this tutorial, you’ll learn how to use the Python string casefold()<\/code> method to carry a case-insensitive string comparison.<\/p>\n\n\n\n

Introduction to the Python string casefold() method #<\/a><\/h2>\n\n\n\n

The Python string casefold()<\/code> method returns a casefolded copy of the string<\/a>.<\/p>\n\n\n\n

Casefolding is like case lowering. However, casefolding is more aggressive because it’s intended to remove all case distinctions in a string.<\/p>\n\n\n\n

If you use purely ASCII text, the lower()<\/a><\/code> and casefold()<\/code> methods return the same result.<\/p>\n\n\n\n

However, if you deal with Unicode characters, the casefold()<\/code> method returns a more accurate result than the lower()<\/code> method.<\/p>\n\n\n\n

For example, the letter '\u00df'<\/code> in Germany is equivalent to 'ss'<\/code>. If you use the lower()<\/code> method, the result would be '\u00df'<\/code> because the letter '\u00df'<\/code> is already lowercase.<\/p>\n\n\n\n

However, if you call the casefold()<\/code> method on the string '\u00df'<\/code>, it would return the 'ss'<\/code> instead.<\/p>\n\n\n\n

For this reason, you should use the string casefold()<\/code> method to carry case-insensitive string comparisons to achieve a more accurate result.<\/p>\n\n\n\n

Python string casefold() method example #<\/a><\/h2>\n\n\n\n

The following example illustrates how to use the lower()<\/code> and casefold()<\/code> methods to compare string case-insensitively:<\/p>\n\n\n

color1 = 'wei\u00df'<\/span>\ncolor2 = 'weiss'<\/span>\n\nprint<\/span>(color1 == color2)  # False<\/span>\nprint<\/span>(color1.lower() == color2.lower())  # False<\/span>\nprint<\/span>(color1.casefold() == color2.casefold())  # True<\/span><\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
Output:<\/p>\n\n\n
False<\/span>\nFalse<\/span>\nTrue<\/span><\/code><\/span>Code language:<\/span> PHP<\/span> (<\/span>php<\/span>)<\/span><\/small><\/pre>\n\n\n
How it works.<\/p>\n\n\n\n
The following expression returns False<\/code> because the lower()<\/code> method doesn’t do anything to the letter '\u00df'<\/code>:<\/p>\n\n\n
color1.lower() == color2.lower()<\/code><\/span><\/pre>\n\n\n
However, the following comparison returns True<\/code> because the casefold()<\/code> method returns a copy of the color2<\/code> string with the letter '\u00df'<\/code> converted to 'ss'<\/code><\/p>\n\n\n\n
Summary #<\/a><\/h2>\n\n\n\n
  • Use string lower()<\/code> method to carry case-insensitive string comparisons for strings with ASCII characters.<\/li>
  • Use string casefold()<\/code> method to perform case-insensitive comparisons for strings with Unicode characters.<\/li><\/ul>\n
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