Python Regular Expression

Introduction

 
In the chapter, we will learn to use Regular Expression in Python. 
 

Regular Expression

 
A regular expression is a particular series of characters that allows you to fit or find certain strings or string sets, utilizing a different syntax in a script.
 
Syntax
  • \s — White space characters
  • \S — Non-white space characters
  • \w — Word characters
  • \W — Non-word characters
  • \d — Digit characters
  • \D — Non-digit characters
Methods and Attributes for search characters
  • match() - Determine if the RE matches at the beginning of the string.
  • search() - Scan through a string, looking for any location where this RE matches.
  • findall()- Find all substrings where the RE matches and returns them as a list.
  • finditer()- Find all substrings where the RE matches and returns them as an iterator.
Methods and Attributes for match object instances
  • group() Return the string matched by the RE
  • start() Return the starting position of the match
  • end() Return the ending position of the match
  • span() Return a tuple containing the (start, end) positions of the match
  1. Now I’m giving you some examples of regular expressions in Python.
    1. import re  
    2. message = 'call me at 9785959495'  
    3. regex = re.compile(r'\d+')  
    4. number = regex.search(message)  
    5. print(number.group())  
    Output: 9785959495
     
    Output
     
    According to the above Example show library re is useful for finding numbers in the message. r’\d+’ here r denotes this is a line and r does not perform escape conversion like \d and \d means search digits and + means total digits.
     
  2. Getting All digits from particular statements
    1. import re  
    2. message = 'call me at 9785959495 or 9929892278'  
    3. regex = re.compile(r'\d+')  
    4. number = regex.findall(message)  
    5. print(number) 
    Output : ['9785959495', '9929892278']
     
    Output
     
  3. Getting in multiple groups value
    1. message = 'call me at 9785959495-9929892278'  
    2. regex = re.compile(r'(\d+)-(\d+)')  
    3. number = regex.search(message)  
    4. number.group() 
    Output : '9785959495-9929892278'
    1. number.group(1
    Output: 9785959495
    1. number.group(2
    Output: 9929892278
     
    Output
     
    Output
Python has many methods for regular expression techniques to find or search characters in regular expression library.
 

Conclusion 

 
In the next chapte, we will learn how we can use database with the help of Python.
Author
Neeraj Kumar
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