Why regular Expressions are so powerful?

Regular expression is a sequence of characters that matches the search patterns.

Photo by Olav Ahrens Røtne on Unsplash

Capturing groups

Portions of the patterns that are enclosed in parenthesis.

Let’s say that we have a list of people’s full names.These names are stored as last name, comma, first name.We want to turn this around and create a string that starts with the first name followed by the last name.

import re
def rearrange_name(name):
…. result = re.search(r’^([\w \.-]*), ([\w \.-]*)$’,name)
….if result is None:
……..return name
….return “{} {}”.format(result[2],result[1])
>>>rearrange_name(‘Poudel, Niraj’)
Niraj poudel
>>>rearrange_name(‘Kohli, Virat’)
Virat Kholi
>>>rearrange_name(‘Dhoni, Mahendra S.’)
Mahendra S. Dhoni

Converting a date of yyyy-mm-dd format to dd-mm-yyyy format using regular expression in python.

import re
def change_date_format(dt):
….return re.sub(r’(\d{4})-(\d{1,2})-(\d{1,2})’, ‘\\3-\\2-\\1’, dt)
dt1 = “1999–10–02”

print(“Original date in YYY-MM-DD Format: “,dt1)
Original date in YYY-MM-DD Format: 1999–10–02

print(“New date in DD-MM-YYYY Format: “,change_date_format(dt1))
New date in DD-MM-YYYY Format: 02–10–1999

Extracting a PID Using regexes in Python

import re
log = ‘December 01 05:21:40 my computer bad_process[12345]: Error performing package upgrade’
def extract_pid(log_line):
….regex = r”\[(\d+)\]”
….result = re.search(regex,log_line)
….if result is None:
……..return ‘’
….return result[1]

print(extract_pid(log))
>>>12345