Python RegEx

Regular expressions (RegEx) are sequences of characters that define a search pattern. They are used for searching, manipulating, and validating strings. Python provides the remodule for working with regular expressions. In this lesson, we will cover the basics of using regular expressions in Python.

Basic Patterns

Regular expressions can contain a variety of characters that have special meanings. Some basic patterns include:

  • . - Matches any single character except newline.
  • ^ - Matches the start of the string.
  • $ - Matches the end of the string.
  • * - Matches zero or more occurrences of the preceding character.
  • + - Matches one or more occurrences of the preceding character.
  • ? - Matches zero or one occurrence of the preceding character.
  • [] - Matches any one of the characters inside the brackets.
  • {} - Matches a specific number of occurrences of the preceding character.

Using the re Module

To use regular expressions in Python, you need to import the re module. For example, to search for a pattern in a string:

import re

pattern = r'apple'
text = 'I like apples and oranges.'

if re.search(pattern, text):
    print('Found')
else:
    print('Not found')

Using Patterns

You can use regular expression patterns for various operations, such as searching, replacing, and splitting strings. For example, to replace all occurrences of a pattern in a string:

import re

pattern = r'apple'
text = 'I like apples and oranges.'

new_text = re.sub(pattern, 'banana', text)
print(new_text)

Conclusion

Regular expressions are powerful tools for working with text data in Python. By understanding basic patterns and using the re module, you can perform complex string operations with ease.

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