Python Language Tutorial: Regular Expression

Introduction

Today, I will take a new part of Python for my tutorial series. In this part, you will learn Exception Handling.

I already told you the following:

Python language has very good functions for Regular function and their regular expression also useful for searching a text from any statement.

Today I will give you some examples of the regular expression that may help you easily learn the concept of regular expression according to python. Microsoft Word also has regular expression techniques for searching text in the whole document like the below Image.

Regular Expression 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

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

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.
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']
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

Python has many methods for regular expression techniques to find or search characters in regular expression library.