Regular expression in is a sequence of characters that forms a search pattern.

It is used to confirm whether the string has that particular term or not.

We can easily import regular expression in python.

• [] – A set of characters
• \ – Signals a special sequence.
• . – Any character
• ^ – Starts with
• $ – Ends with
• * – Zero or more occurrence
• + – One or more occurrence
• {} – Exactly the specified number of occurrences.
• | – Either or
• () – Capture and group

Special sequence:-

• \d Matches any decimal digit, this is equivalent to the set class [0-9].
• \D Matches any non-digit character.
• \s Matches any whitespace character.
• \S Matches any non-whitespace character
• \w Matches any alphanumeric character, this is equivalent to the class [a-zA-Z0-9_].
• \W Matches any non-alphanumeric character.

Search function searches the whole string to match the substring and returns its index.

syntax:-

re.search(substring, string, flag)

e.g.,

import re
a="Python"
s=''' One of the most famous programming language in the world is Python.'''
print(re.search(a, s))

This is all about search function in python.