{"id":348,"date":"2024-01-28T11:35:40","date_gmt":"2024-01-28T11:35:40","guid":{"rendered":"https:\/\/learnpython.elegantwallp.com\/?p=348"},"modified":"2024-01-28T11:35:41","modified_gmt":"2024-01-28T11:35:41","slug":"python-regex-quantifiers","status":"publish","type":"post","link":"https:\/\/learnpython.elegantwallp.com\/2024\/01\/28\/python-regex-quantifiers\/","title":{"rendered":"Python Regex Quantifiers"},"content":{"rendered":"\n

Summary<\/strong>: in this tutorial, you\u2019ll learn how to use Python regex quantifiers to define how many times a character or a character set can be repeated.<\/p>\n\n\n\n

Introduction to Python regex quantifiers<\/h2>\n\n\n\n

In\u00a0regular expressions, quantifiers match the preceding characters or character sets a number of times. The following table shows all the quantifiers and their meanings:<\/p>\n\n\n\n

Quantifier<\/th>Name<\/th>Meaning<\/th><\/tr><\/thead>
*<\/code><\/td>Asterisk<\/td>Match its preceding element zero or more times.<\/td><\/tr>
+<\/code><\/td>Plus<\/td>Match its preceding element one or more times.<\/td><\/tr>
?<\/code><\/td>Question Mark<\/td>Match its preceding element zero or one time.<\/td><\/tr>
{<\/code> n<\/em> }<\/code><\/td>Curly Braces<\/td>Match its preceding element exactly n<\/code> times.<\/td><\/tr>
{<\/code> n<\/em> ,}<\/code><\/td>Curly Braces<\/td>Match its preceding element at least n<\/code> times.<\/td><\/tr>
{<\/code> n<\/em> ,<\/code> m<\/em> }<\/code><\/td>Curly Braces<\/td>Match its preceding element from n<\/code> to m<\/code> times.<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n

Match zero or more times (*<\/code>)<\/h3>\n\n\n\n

The quantifier (*<\/code>) matches its preceding element zero or more times. For example, the following program uses the\u00a0*<\/code>\u00a0quantifier to match any string that ends with\u00a0Python<\/code>:<\/p>\n\n\n\n

import re s = \"\"\"CPython, IronPython, and JPython are major Python's implementation\"\"\" matches = re.finditer('\\w*Python', s) for match in matches: print(match)<\/code>Code language: Python (python)<\/small><\/code><\/pre>\n\n\n\n
In this example:<\/p>\n\n\n\n
    \n
  • The \\w<\/code> matches any single word character.<\/li>\n\n\n\n
  • So the \\w*<\/code> matches zero or more word characters.<\/li>\n\n\n\n
  • Therefore, the \\w*Python<\/code> match any zero or more characters followed by the string Python<\/code>.<\/li>\n<\/ul>\n\n\n\n
    As a result, the\u00a0\\w*Python<\/code>\u00a0pattern matches\u00a0CPython<\/code>,\u00a0IronPython<\/code>,\u00a0JPython<\/code>, and\u00a0Python<\/code>\u00a0in the string:<\/p>\n\n\n\n
    <re.Match object; span=(0, 7), match='CPython'> <re.Match object; span=(9, 19), match='IronPython'> <re.Match object; span=(25, 32), match='JPython'> <re.Match object; span=(51, 57), match='Python'> <\/code>Code language: Python (python)<\/small><\/code><\/pre>\n\n\n\n
    Match one or more times (+<\/code>)<\/h3>\n\n\n\n
    The +<\/code> quantifier matches its preceding element one or more times. For example, the \\d+<\/code> matches one or more digits.<\/p>\n\n\n\n
    The following example uses the\u00a0+<\/code>\u00a0quantifier to match one or more digits in a string:<\/p>\n\n\n\n
    import re s = \"Python 3.10 was released in 2021\" matches = re.finditer('\\d+', s) for match in matches: print(match)<\/code>Code language: Python (python)<\/small><\/code><\/pre>\n\n\n\n
    Output:<\/p>\n\n\n\n
    <re.Match object; span=(7, 8), match='3'> <re.Match object; span=(9, 11), match='10'> <re.Match object; span=(28, 32), match='2021'><\/code>Code language: Python (python)<\/small><\/code><\/pre>\n\n\n\n
    Match zero or one time (?<\/code>)<\/h3>\n\n\n\n
    The ?<\/code> quantifier matches its preceding element zero or one time.<\/p>\n\n\n\n
    The following example uses the (?) quantifier to match both strings\u00a0color<\/code>\u00a0and\u00a0colour<\/code>:<\/p>\n\n\n\n
    import re s = \"What color \/ colour do you like?\" matches = re.finditer('colou?r', s) for match in matches: print(match)<\/code>Code language: Python (python)<\/small><\/code><\/pre>\n\n\n\n
    Output:<\/p>\n\n\n\n
    <re.Match object; span=(5, 10), match='color'> <re.Match object; span=(13, 19), match='colour'><\/code>Code language: Python (python)<\/small><\/code><\/pre>\n\n\n\n
    In this example, the u?<\/code> matches zero or one character u<\/code>. Therefore, the colou?r<\/code> pattern matches both color<\/code> and colour<\/code><\/p>\n\n\n\n
    Match Exactly n Times: {n}<\/h3>\n\n\n\n
    The {n}<\/code> quantifier matches its preceding element exactly n<\/code> times, where n<\/code> is zero or a positive integer.<\/p>\n\n\n\n
    For example, the following program uses the quantifier\u00a0{n}<\/code>\u00a0to match a time string in the\u00a0hh:mm<\/code>\u00a0format:<\/p>\n\n\n\n
    import re s = \"It was 11:05 AM\" matches = re.finditer('\\d{2}:\\d{2}', s) for match in matches: print(match)<\/code>Code language: Python (python)<\/small><\/code><\/pre>\n\n\n\n
    Output:<\/p>\n\n\n\n
    <re.Match object; span=(7, 12), match='11:05'><\/code>Code language: Python (python)<\/small><\/code><\/pre>\n\n\n\n
    In this example, the \\d{2}<\/code> matches exactly two digits. Therefore, the \\d{2}:\\d{2}<\/code> matches a string that starts with two digits, a colon :<\/code>, and ends with two digits.<\/p>\n\n\n\n
    Match at least n times: {n,}<\/h3>\n\n\n\n
    The {n,}<\/code> quantifier matches its preceding element at least n<\/code> times, where n<\/code> is zero or a positive integer.<\/p>\n\n\n\n
    For example, the following program uses the\u00a0{n, }<\/code>\u00a0quantifier to match the date strings with the\u00a0m-d-yyyy<\/code>\u00a0or\u00a0mm-dd-yyyy<\/code>\u00a0format:<\/p>\n\n\n\n
    import re s = \"5-5-2021 or 05-05-2021 or 5\/5\/2021\" matches = re.finditer('\\d{1,}-\\d{1,}-\\d{4}', s) for match in matches: print(match)<\/code>Code language: Python (python)<\/small><\/code><\/pre>\n\n\n\n
    Output:<\/p>\n\n\n\n
    <re.Match object; span=(0, 8), match='5-5-2021'> <re.Match object; span=(12, 22), match='05-05-2021'><\/code>Code language: Python (python)<\/small><\/code><\/pre>\n\n\n\n
    Match from n and m times: {n,m}<\/h3>\n\n\n\n
    The\u00a0{n,m}<\/code>\u00a0quantifier matches its preceding element at least\u00a0n<\/code>\u00a0times, but no more than\u00a0m<\/code>\u00a0times, where\u00a0n<\/code>\u00a0and\u00a0m<\/code>\u00a0are zero or a positive integer. For example:<\/p>\n\n\n\n
    import re s = \"5-5-2021 or 05-05-2021 or 5\/5\/2021\" matches = re.finditer('\\d{1,2}-\\d{1,2}-\\d{4}', s) for match in matches: print(match)<\/code>Code language: Python (python)<\/small><\/code><\/pre>\n\n\n\n
    Output:<\/p>\n\n\n\n
    <re.Match object; span=(0, 8), match='5-5-2021'> <re.Match object; span=(12, 22), match='05-05-2021'><\/code>Code language: Python (python)<\/small><\/code><\/pre>\n\n\n\n
    In this example, the pattern \\d{1,2}<\/code> matches one or two digits. So the pattern \\d{1,2}-\\d{1,2}-\\d{4}<\/code> matches a date string in the d-m-yyyy<\/code> or dd-mm-yyyy<\/code> format.<\/p>\n","protected":false},"excerpt":{"rendered":"
    Summary: in this tutorial, you\u2019ll learn how to use Python regex quantifiers to define how many times a character or a character set can be repeated. Introduction to Python regex quantifiers In\u00a0regular expressions, quantifiers match the preceding characters or character sets a number of times. The following table shows all the quantifiers and their meanings: […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[42],"tags":[],"class_list":["post-348","post","type-post","status-publish","format-standard","hentry","category-2-python-regex"],"_links":{"self":[{"href":"https:\/\/learnpython.elegantwallp.com\/wp-json\/wp\/v2\/posts\/348","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/learnpython.elegantwallp.com\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/learnpython.elegantwallp.com\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/learnpython.elegantwallp.com\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/learnpython.elegantwallp.com\/wp-json\/wp\/v2\/comments?post=348"}],"version-history":[{"count":1,"href":"https:\/\/learnpython.elegantwallp.com\/wp-json\/wp\/v2\/posts\/348\/revisions"}],"predecessor-version":[{"id":349,"href":"https:\/\/learnpython.elegantwallp.com\/wp-json\/wp\/v2\/posts\/348\/revisions\/349"}],"wp:attachment":[{"href":"https:\/\/learnpython.elegantwallp.com\/wp-json\/wp\/v2\/media?parent=348"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/learnpython.elegantwallp.com\/wp-json\/wp\/v2\/categories?post=348"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/learnpython.elegantwallp.com\/wp-json\/wp\/v2\/tags?post=348"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}