In this article we will learn about Python RegEx
Python RegEx – Before moving ahead let’s know a little bit about Python JSON
RegEx – RegEx (Regular Expression), It is a sequence of character that finds a way of the searching pattern. it can also be used to check if a specified string is present in the given string or not.
RegEx Module – To use RegEx, import Python’s built-in module called re.
Import the re module.
import re
Example 1- Search if the string contains the specified element and ends with specified element.
import re x = 'Hello! How are you doing?' z = re.search('^Hello,*doing? $', x) if z: print('Match found') else: print('No match found')

Explanation – As shown clearly, a match was not found; therefore, it returned else statement.
Example 2 – Search if the string contains the specified element and ends with specified element.
import re x = 'Hello! How are you doing?' z = re.search("are", x) if z: print('Match found') else: print('No match found')

Explanation – As shown clearly, a match was found; therefore, it returned if statement.
RegEx Functions – The re module contains a set of functions that allows searching a string for a match.
This set of function follows as –
1. findall() function – It returns a list containing specified matches.
Example 1- It returns a list of every occurrence of specified match.
import re x = 'Hello! How are you doing?' z = re.findall('Hello How are you doing?', x) print(z)

Explanation – As shown clearly, a match was found; therefore, it returned string in the list.
Note: If it doesn’t contain specified match, then it returns an empty list.
Example 2- It returns an empty list.
import re x = 'Hello! How are you doing?' z = re.findall('Good', x) print(z)

Explanation – As shown clearly, a match was not found; therefore, it returned an empty list.
2. search() function – It searches the string for a match and returns the match object if there is a match.
Note: In case there is more than one match, only the first occurrence of the match is returned.
Example 1- It returns the match object (index number) of specified string.
import re x = "Hello, Alex" z = re.search('ex', x) print(z)

Explanation – As shown clearly, a match was found; therefore, it returned a match string with its index number (start and end).
Note: If no match is found, the value None is returned.
Example 2- It returns None.
import re x = "Hello, Alex" z = re.search('Gh' , x) print(z)

Explanation – As shown clearly, a match was not found; therefore, it returned None.
3. split() function – It returns the list of spilt string at each match.
Example 1- Split the string at each match.
import re x = 'Hello! Jello' z = re.split('lo' , x) print(z)

Explanation – As shown clearly, a match was found; therefore, it returned split the string.
Note: By specifying maxsplit parameter, number of occurrences can be controlled.
Example 2- Split the string at first occurrence of specified string.
import re x = 'Hello! Jello, Sello' z = re.split('lo' , x , 1) print(z)

Explanation – As shown clearly, a match was found; therefore, it returned split character only with the first occurrence of a character.
Example 3- Check if string can be split or not.
import re x = 'Hello! Jello' z = re.split('&' , x) print(z)

Explanation – As shown clearly, a match was not found; therefore, it returned the original string.
4. sub() function – It replaces all matches with the specified text.
Example 1- It replaces all matches with the string ‘li’.
import re x = 'Hello! Jello, Sello' z = re.sub('lo' , 'li' , x) print(z)

Explanation – As shown clearly, a match was found; therefore, it returned replaced string.
Note: Use of count parameter to control the number of occurrences.
Example 2- It replaces first two matches with the string ‘li’.
import re x = 'Hello! Jello, Sello' z = re.sub('lo' , 'li' , x , 2) print(z)

Explanation – As shown clearly, a match was found; therefore, it returned replaced the first two specified strings.
Example 3 – Check if it replaces all matches with the string or not.
import re x = 'Hello! Jello, Sello' z = re.sub('Lo', 'li', x) print(z)

Explanation – As shown clearly, a match was not found; therefore, it returned original strings.
If you find anything incorrect in the above-discussed topic and have any further questions, please comment down below.
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