Python RegEx

Python Tutorial � Python RegEx

RegEx (Regular Expression) is a sequence of characters what defines a search pattern.
Pattern is: any five letter string starting with a and ending with s.

Example:

^a...s$

How we use RegEx in Python - example

Python has a module re working with RegEx.
Method used returns a match object if the search is successful.

Example:

import re

#Check if the string starts with "Now" and ends with "home":
my_txt = "Now with a lot of web pages I can learn PYTHON from home"
y = re.search("^Now.*home$", my_txt)

if y:
��print("YES! We have a match! my_string: Now with a lot of web pages I can learn PYTHON from home")
else:
��print("No match")

Output:
YES! We have a match! my_string: Now with a lot of web pages I can learn PYTHON from home

RegEx Functions

findall Returns a list containing all matches
search Returns a Match object if there is a match anywhere in the string
split Returns a list where the string has been split at each match
sub Replaces one or many matches with a string

The findall() Function - Returns a list containing all matches

Example: findall() Function

import re

#Check if a list contain "a lot":
my_txt = "Now with a lot of web pages I can learn a lot of PYTHON from home"
y = re.findall("a lot", my_txt)

if y:
print(y)
else:
print("No match")

Output:
['a lot', 'a lot']

"search" Function Returns a Match object if there is a match anywhere in the string

Example:

import re

my_txt = "Now-with a lot of web pages I can learn a lot of PYTHON from home"
y = re.search("\s", my_txt)

print("The first white-space character is located in position:", y.start())

Output:
The first white-space character is located in position: 8

split() Function

Example:

import re

#Split the string at every white-space character:

my_txt = "Now-with a lot of web pages I can learn a lot of PYTHON from home"
y = re.split("\s", my_txt)
print(y)

Output:
['Now-with', 'a', 'lot', 'of', 'web', 'pages', 'I', 'can', 'learn', 'a', 'lot', 'of', 'PYTHON', 'from', 'home']

sub() Function

Example: Create an alias for my_file called filexx:

import re

#Replace all white-space characters with the digit "--":

my_txt = "Now-with a lot of web pages I can learn a lot of PYTHON from home"
y = re.sub("\s", "--", my_txt)
print(y)

Output:
Now-with--a--lot--of--web--pages--I--can--learn--a--lot--of--PYTHON--from--home

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Python RegEx - python

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