{"id":3175,"date":"2021-11-30T04:27:05","date_gmt":"2021-11-30T04:27:05","guid":{"rendered":"https:\/\/www.pythontutorial.net\/?page_id=3175"},"modified":"2021-12-03T08:09:13","modified_gmt":"2021-12-03T08:09:13","slug":"python-regex-non-greedy","status":"publish","type":"page","link":"https:\/\/www.pythontutorial.net\/python-regex\/python-regex-non-greedy\/","title":{"rendered":"Python Regex Non-Greedy"},"content":{"rendered":"\n

Summary<\/strong>: in this tutorial, you’ll learn about the regex non-greedy (or lazy) quantifiers that match their preceding elements as few times as possible.<\/p>\n\n\n\n

Introduction to the regex non-greedy (or lazy) quantifiers #<\/a><\/h2>\n\n\n\n

Quantifiers<\/a> allow you to match their preceding elements a number of times. Quantifiers work in one of two modes: greedy<\/a> and non-greedy (lazy).<\/p>\n\n\n\n

When quantifiers work in the greedy mode, they are called greedy quantifiers. Similarly, when quantifiers work in the non-greedy mode, they’re called non-greedy quantifiers or lazy quantifiers.<\/p>\n\n\n\n

By default, quantifiers work in the greedy mode. It means the greedy quantifiers will match their preceding elements as much as possible to return to the biggest match possible.<\/p>\n\n\n\n

On the other hand, the non-greedy quantifiers will match as little as possible to return the smallest match possible. non-greedy quantifiers are the opposite of greedy ones.<\/p>\n\n\n\n

To turn greedy quantifiers into non-greedy quantifiers, you add an extra question mark (?<\/code>) to the quantifiers. The following table shows the greedy and their corresponding non-greedy quantifiers:<\/p>\n\n\n\n

Greedy quantifier<\/th>Lazy quantifier<\/th>Meaning<\/th><\/tr><\/thead>
*<\/code><\/td>*?<\/code><\/td>Match its preceding element zero or more times.<\/td><\/tr>
+<\/code><\/td>+?<\/code><\/td>Match its preceding element one or more times.<\/td><\/tr>
?<\/code><\/td>??<\/code><\/td>Match its preceding element zero or one time.<\/td><\/tr>
{<\/code> n<\/em> }<\/code><\/td>{<\/code> n<\/em> }?<\/code><\/td>Match its preceding element exactly n<\/em> times.<\/td><\/tr>
{<\/code> n<\/em> ,}<\/code><\/td>{<\/code> n<\/em> ,}?<\/code><\/td>Match its preceding element at least n<\/em> times.<\/td><\/tr>
{<\/code> n<\/em> ,<\/code> m<\/em> }<\/code><\/td>{<\/code> n<\/em> ,<\/code> m<\/em> }?<\/code><\/td>Match its preceding element from n<\/em> to m<\/em> times.<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n

Python regex non-greedy quantifiers example #<\/a><\/h2>\n\n\n\n

The following program uses the non-greedy quantifier (+?<\/code>) to match the text within the quotes (\"\"<\/code>) of a button element:<\/p>\n\n\n

import<\/span> re\n\ns = '<button type=\"submit\" class=\"btn\">Send<\/button>'<\/span>\n\npattern = '\".+?\"'<\/span>\nmatches = re.finditer(pattern, s)\n\nfor<\/span> match in<\/span> matches:\n    print(match.group())\n<\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
Output:<\/p>\n\n\n
\"submit\"<\/span>\n\"btn\"<\/span><\/code><\/span>Code language:<\/span> Python<\/span> (<\/span>python<\/span>)<\/span><\/small><\/pre>\n\n\n
Summary #<\/a><\/h2>\n\n\n\n
  • Non-greedy quantifiers match their preceding elements as little as possible to return the smallest possible match.<\/li>
  • Add a question mark (?) to a quantifier to turn it into a non-greedy quantifier.<\/li><\/ul>\n
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    Was this tutorial helpful ?<\/div>\n\t\t
    \n\t\t\t\n\t\t\t\t\n\t\t\t\t\t<\/path>\n\t\t\t\t<\/svg>\n\t\t\t\t Yes <\/span>\n\t\t\t<\/button>\n\n\t\t\t\n\t\t\t\t\n\t\t\t\t\t<\/path>\n\t\t\t\t<\/svg>\n\t\t\t\t No <\/span>\n\t\t\t<\/button>\n\t\t<\/div>\n\t<\/header>\n\n\t
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