{"id":598,"date":"2024-11-28T06:18:01","date_gmt":"2024-11-28T06:18:01","guid":{"rendered":"https:\/\/techkubo.com\/python\/?p=598"},"modified":"2025-06-23T15:02:06","modified_gmt":"2025-06-23T15:02:06","slug":"python-regex","status":"publish","type":"post","link":"https:\/\/techkubo.com\/python\/python-regex\/","title":{"rendered":"Python RegEx"},"content":{"rendered":"\n

Regular expressions, often abbreviated as regex, are a powerful tool for matching patterns in strings. Python’s re<\/code> module provides a set of functions that allows you to search a string for a match using a regular expression. This lesson will introduce you to the basics of using regular expressions in Python.<\/p>\n\n\n\n

What are Regular Expressions?<\/strong><\/h2>\n\n\n\n

Regular expressions are sequences of characters that form search patterns. They can be used to check if a string contains a specific pattern, extract parts of the string, and replace parts of the string with other text.<\/p>\n\n\n\n

The re<\/code> Module<\/strong><\/h2>\n\n\n\n

To work with regular expressions in Python, you need to import the re<\/code> module:<\/p>\n\n\n\n

import re<\/pre><\/div>\n\n\n\n
<\/p>\n\n\n\n
Common Functions in re<\/code><\/strong><\/h2>\n\n\n\n
    \n
  • re.match()<\/code><\/strong>: Determines if the RE matches at the beginning of the string.<\/li>\n\n\n\n
  • re.search()<\/code><\/strong>: Scans through a string, looking for any location where this RE matches.<\/li>\n\n\n\n
  • re.findall()<\/code><\/strong>: Finds all the matches and returns them as a list.<\/li>\n\n\n\n
  • re.sub()<\/code><\/strong>: Replaces occurrences of a pattern found in the string.<\/li>\n<\/ul>\n\n\n\n
    Regular Expression Patterns<\/strong><\/h2>\n\n\n\n
      \n
    • Literal characters<\/strong>: Simply match themselves. Example: abc<\/code> matches ‘abc’.<\/li>\n\n\n\n
    • Dot (.<\/code>)<\/strong>: Matches any character except a newline.<\/li>\n\n\n\n
    • Character classes ([]<\/code>)<\/strong>: Matches any single character within the brackets. Example: [a-z]<\/code> matches any lowercase letter.<\/li>\n\n\n\n
    • Quantifiers (*<\/code>, +<\/code>, ?<\/code>, {}<\/code>)<\/strong>: Specify the number of occurrences to match.<\/li>\n\n\n\n
    • *<\/code> matches 0 or more occurrences.<\/li>\n\n\n\n
    • +<\/code> matches 1 or more occurrences.<\/li>\n\n\n\n
    • ?<\/code> matches 0 or 1 occurrence.<\/li>\n\n\n\n
    • {m,n}<\/code> matches between m and n occurrences.<\/li>\n<\/ul>\n\n\n\n
      Python RegEx Examples<\/strong><\/h2>\n\n\n\n
      Example 1: Matching a Phone Number<\/strong><\/p>\n\n\n\n
      import re\n\npattern = r'\\d{3}-\\d{2}-\\d{4}'\ntext = 'My phone number is 123-45-6789'\n\nmatch = re.match(pattern, text)\nif match:\n    print("Match found!")\nelse:\n    print("No match found.")<\/pre><\/div>\n\n\n\n
      Example 2: Finding All Numbers<\/strong><\/p>\n\n\n\n
      import re\n\npattern = r'\\d+'\ntext = 'There are 123 apples and 45 oranges'\n\nmatches = re.findall(pattern, text)\nprint(matches)  # Output: ['123', '45']<\/pre><\/div>\n\n\n\n
      Example 3: Replacing White Spaces<\/strong><\/p>\n\n\n\n
      import re\n\npattern = r'\\s'\nreplacement = '-'\ntext = 'Hello World'\n\nnew_text = re.sub(pattern, replacement, text)\nprint(new_text)  # Output: 'Hello-World'<\/pre><\/div>\n\n\n\n
      <\/p>\n\n\n\n
      Python Labs<\/strong><\/h2>\n\n\n\n