Regular Expression in Python

In this tutorial, we will focus on Regular expression in Python with some examples.

Regular Expression in Python with examples

A regular expression is a group of a special sequence of characters that can be used to match or detect other strings.

Many basic patterns can be easily tackled using these special characters.

Regular Expression -Character classes: in Python

1.[abc] =could be a ,b or c
2.[^abc] = Except a , b or c
3.[a-z] = Any lower case alphabet symbol
4.[A-Z] = Any upper case alphabet symbol
5.[a-zA-z] Any alphabet symbols
6.[0-9] = any digits from 0 to 9
7.[a-zA-Z0-9] - Any alphanumeric character
8.[^a-zA-Z0-9] - Except alphanumeric character (special character).

9. \s - Space character
10.\S - Any character Except space character
11.\d - Any digit from 0 to 9
12.\D - any character except digit
13.\w - any word character[a-zA-Z0-9]
14.\W - Any character except word character (Special character).

 

Various methods of Regular Expression-

  1. re.match()
  2. re.search()
  3. re.findall()
  4. re.split()
  5. re.sub()
  6. re.compile()

Example-




Valid mail id or not- Regular expression

import re
choice="y"
while choice=="y":
    email =input("Enter email id")
    match = re.match('^[_a-z0-9]+(\.[_a-z0-9]+)*@[a-z]+(\.[a-z]+)*(\.[a-z]{2,4})$', email)
    if match == None:
        print('Bad Syntax')
    else:
        print("valid mail id")

Output-

Enter email id-123gmail.com
Bad Syntax
Enter email [email protected]
valid mail id

Example 2 Regular expression

import re

result = re.search('Code', 'Code Speedy')

print (result.group(0))

Output-

Code

Example 3

import re
result = re.findall('Earth', 'Earth is large and Earth is unique')

print (result)
Output-
['Earth', 'Earth']

Example 4

import re
result=re.split('e','Code Speedy')

print(result)

Output-

['Cod', ' Sp', '', 'dy']

Example 5-

import re

result=re.split('h','Earth is round')

print(result)
Output:
['Eart', ' is round']

Example 6-

import re

obj=re.compile('kanto')

result=obj.findall('Ash is from kanto')

print (result)

result2=obj.findall('kanto  is largest region  of all')

print (result2)

Output:

['kanto']
['kanto']

Return the first two character of each word- in Python using Regular expression

import re
result=re.findall(\w\w','Largest community of India')
print (result)

Output-

['la', 'rg', 'es', 'co', 'mm', 'un', 'it', 'of', 'In', 'di']

^ symbols-

We can use ^ symbol to check whether the given target string starts with our provided patters or not.

import re
s="Learning Python is very easy"
res=re.search("^Learn",s)
if res!=None:
print("Target String starts with Learn")
else:
print("Target String not starts with Learn")

$ symbol-

We can use the $ symbol to check whether the given target string ends with our provided pattern or not.

import re
s="Learning Python is very easy"
res=re.search("easy$",s)
if res!=None:
print("Target String ends with easy")
else:
print("Target String not ends with easy")

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