{"id":86,"date":"2025-10-25T06:47:09","date_gmt":"2025-10-25T06:47:09","guid":{"rendered":"https:\/\/codetypingpro.com\/?p=86"},"modified":"2025-12-17T07:49:06","modified_gmt":"2025-12-17T07:49:06","slug":"regular-expressions","status":"publish","type":"post","link":"https:\/\/codetypingpro.com\/?p=86","title":{"rendered":"Lesson 21: Regular Expressions in Python"},"content":{"rendered":"\n

<\/h2>\n\n\n\n

\ud83c\udfaf Lesson Objective<\/strong><\/h3>\n\n\n\n

To understand and apply Regular Expressions (RegEx)<\/strong> in Python for searching, validating, and manipulating text patterns efficiently.<\/p>\n\n\n\n

\n\n\n\n

\ud83e\udde9 1. What Are Regular Expressions?<\/strong><\/h2>\n\n\n\n

Regular Expressions (RegEx)<\/strong> are special patterns used to match strings or parts of strings.
Python provides the re<\/code><\/strong> module to work with these expressions.<\/p>\n\n\n\n

\u2705 Importing RegEx Module:<\/strong><\/p>\n\n\n\n

import re\n<\/code><\/pre>\n\n\n\n
\n\n\n\n
\u2699\ufe0f 2. Common RegEx Functions<\/strong><\/h2>\n\n\n\n
Function<\/th>Description<\/th><\/tr><\/thead>
re.search()<\/code><\/td>Finds the first match<\/strong> in a string<\/td><\/tr>
re.findall()<\/code><\/td>Returns all matches<\/strong> as a list<\/td><\/tr>
re.match()<\/code><\/td>Checks if string starts<\/strong> with the pattern<\/td><\/tr>
re.split()<\/code><\/td>Splits string by the matched pattern<\/td><\/tr>
re.sub()<\/code><\/td>Replaces pattern with a new string<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n
\n\n\n\n
\ud83d\udd0d 3. Basic Examples<\/strong><\/h2>\n\n\n\n
Example 1 \u2013 search()<\/code><\/h3>\n\n\n\n
import re\ntext = \"My phone number is 9876543210\"\npattern = r\"\\d{10}\"\nmatch = re.search(pattern, text)\nprint(match.group())\n<\/code><\/pre>\n\n\n\n
Output:<\/strong><\/p>\n\n\n\n
9876543210\n<\/code><\/pre>\n\n\n\n
\n\n\n\n
Example 2 \u2013 findall()<\/code><\/h3>\n\n\n\n
text = \"Emails: user1@gmail.com, user2@yahoo.com\"\nemails = re.findall(r'\\S+@\\S+', text)\nprint(emails)\n<\/code><\/pre>\n\n\n\n
Output:<\/strong><\/p>\n\n\n\n
['user1@gmail.com', 'user2@yahoo.com']\n<\/code><\/pre>\n\n\n\n
\n\n\n\n
Example 3 \u2013 match()<\/code><\/h3>\n\n\n\n
text = \"Python is powerful\"\nresult = re.match(r\"Python\", text)\nprint(result)\n<\/code><\/pre>\n\n\n\n
Output:<\/strong><\/p>\n\n\n\n
<re.Match object; span=(0, 6), match='Python'>\n<\/code><\/pre>\n\n\n\n
\n\n\n\n
Example 4 \u2013 split()<\/code><\/h3>\n\n\n\n
text = \"apple,banana;orange grape\"\nwords = re.split(r'[;,\\s]+', text)\nprint(words)\n<\/code><\/pre>\n\n\n\n
Output:<\/strong><\/p>\n\n\n\n
['apple', 'banana', 'orange', 'grape']\n<\/code><\/pre>\n\n\n\n
\n\n\n\n
Example 5 \u2013 sub()<\/code><\/h3>\n\n\n\n
text = \"My number is 9876543210\"\nnew_text = re.sub(r'\\d+', '**********', text)\nprint(new_text)\n<\/code><\/pre>\n\n\n\n
Output:<\/strong><\/p>\n\n\n\n
My number is **********\n<\/code><\/pre>\n\n\n\n
\n\n\n\n
\ud83e\uddf1 4. Common RegEx Patterns<\/strong><\/h2>\n\n\n\n
Pattern<\/th>Meaning<\/th>Example Match<\/th><\/tr><\/thead>
\\d<\/code><\/td>Digit (0\u20139)<\/td>3<\/td><\/tr>
\\D<\/code><\/td>Non-digit<\/td>A<\/td><\/tr>
\\w<\/code><\/td>Word character (a\u2013z, 0\u20139, _)<\/td>a<\/td><\/tr>
\\W<\/code><\/td>Non-word character<\/td>@<\/td><\/tr>
\\s<\/code><\/td>Whitespace<\/td>(space, tab)<\/td><\/tr>
^<\/code><\/td>Start of string<\/td>^Python<\/code><\/td><\/tr>
$<\/code><\/td>End of string<\/td>end$<\/code><\/td><\/tr>
.<\/code><\/td>Any character (except newline)<\/td>c.t<\/code> \u2192 cat, cot<\/td><\/tr>
*<\/code><\/td>0 or more repetitions<\/td>lo*l<\/code> \u2192 ll, lol, loool<\/td><\/tr>
+<\/code><\/td>1 or more repetitions<\/td>go+<\/code> \u2192 go, goo, gooo<\/td><\/tr>
{n}<\/code><\/td>Exactly n times<\/td>\\d{4}<\/code> \u2192 2025<\/td><\/tr>
`<\/td>`<\/td>OR condition<\/td><\/tr>
[]<\/code><\/td>Character set<\/td>[A-Z]<\/code> matches A\u2013Z<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n
\n\n\n\n
\ud83e\udde0 5. Real-Life Use Cases<\/strong><\/h2>\n\n\n\n
    \n
  • Validate email<\/strong>, phone number<\/strong>, or passwords<\/strong><\/li>\n\n\n\n
  • Extract data<\/strong> from text (e.g., IDs, numbers, dates)<\/li>\n\n\n\n
  • Find or replace text in logs or documents<\/li>\n\n\n\n
  • Split structured text (CSV, JSON strings)<\/li>\n<\/ul>\n\n\n\n
    \n\n\n\n
    \ud83c\udf0d 6. Real-Life Example \u2013 Email Validation<\/strong><\/h2>\n\n\n\n
    import re\n\nemail = \"sameer123@gmail.com\"\npattern = r'^[a-zA-Z0-9._]+@[a-z]+\\.[a-z]+$'\n\nif re.match(pattern, email):\n    print(\"Valid email address!\")\nelse:\n    print(\"Invalid email address!\")\n<\/code><\/pre>\n\n\n\n
    Output:<\/strong><\/p>\n\n\n\n
    Valid email address!\n<\/code><\/pre>\n\n\n\n
    \n\n\n\n
    \ud83d\udcac 7. Password Strength Validation<\/strong><\/h2>\n\n\n\n
    password = \"Pa$$word123\"\npattern = r'^(?=.*[A-Z])(?=.*[a-z])(?=.*\\d)(?=.*[@$!%*?&])[A-Za-z\\d@$!%*?&]{8,}$'\n\nif re.match(pattern, password):\n    print(\"Strong password!\")\nelse:\n    print(\"Weak password!\")\n<\/code><\/pre>\n\n\n\n
    Output:<\/strong><\/p>\n\n\n\n
    Strong password!\n<\/code><\/pre>\n","protected":false},"excerpt":{"rendered":"
    \ud83c\udfaf Lesson Objective To understand and apply Regular Expressions (RegEx) in Python for searching, validating, and manipulating text patterns efficiently. \ud83e\udde9 1. What Are Regular Expressions? Regular Expressions (RegEx) are special patterns used to match strings or parts of strings.Python provides the re module to work with these expressions. \u2705 Importing RegEx Module: \u2699\ufe0f 2. […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[6,1],"tags":[],"class_list":["post-86","post","type-post","status-publish","format-standard","hentry","category-python-easy-course-outline","category-uncategorized"],"_links":{"self":[{"href":"https:\/\/codetypingpro.com\/index.php?rest_route=\/wp\/v2\/posts\/86","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/codetypingpro.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/codetypingpro.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/codetypingpro.com\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/codetypingpro.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=86"}],"version-history":[{"count":2,"href":"https:\/\/codetypingpro.com\/index.php?rest_route=\/wp\/v2\/posts\/86\/revisions"}],"predecessor-version":[{"id":93,"href":"https:\/\/codetypingpro.com\/index.php?rest_route=\/wp\/v2\/posts\/86\/revisions\/93"}],"wp:attachment":[{"href":"https:\/\/codetypingpro.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=86"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/codetypingpro.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=86"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/codetypingpro.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=86"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}