Explain the Python RegEx with Example

Question

Mayank kumar Verma · Answer

Regex is a super smart search tool to finding patterns in text like email, phone number etc.
Basic stepupand 
pythone
import re
4 Main Functions You Needand 
1 Find if exists - re. search ()
Python
text = “My number is 9876543210”
2 Find ALLand 
python
re.findall(r'\d+', and “I have 2 cats, 3 dogs”) and # ['2', ‘3’,]
3 Replace
python
re.sub(r'\d', 'X', "Call 123") # Call XXX
Key Patterns:
\d = digit (0-9)
\w = letter
\s = space
+ = one or moreand 
Example
python
emport and re
text = "Email: john@site.com"
email = re.findall(r'\S+@\S+', text)
print(email) and #[ ‘jhon@site.com’ ]
Done.

Anubhav Kumar · Answer

What is RegEx?
RegEx (Regular Expression) is a 
pattern-matching language used to find, search, or manipulate text (strings).
Python has a built-in 
module for RegEx:
import re
Common RegEx Functions in Python (re module)
Function
Description
re.match()
Matches pattern only at the beginning of a string
re.search()
Searches for a pattern anywhere in the string
re.findall()
Returns all matches in a list
re.finditer()
Returns iterator of match objects
re.sub()
Replaces matches with another string
re.split()
Splits a string by the pattern
Basic Syntax
Symbol
Meaning
Example
Matches
.
Any character (except newline)
a.c
“abc”, “axc”
^
Start of string
^Hello
“Hello world”
$
End of string
world$
“Hello world”
*
0 or more repetitions
go*d
“gd”, “god”, “good”
+
1 or more repetitions
go+d
“god”, “good”
?
0 or 1 repetition
go?d
“gd”, “god”
{n}
Exactly n times
\d{3}
“123”
{n,m}
Between n and m times
\d{2,4}
“12”, “1234”
[]
Any one of listed characters
[aeiou]
Any vowel
\d
Any digit
\d
“0–9”
\w
Any word char (a–z, A–Z, 0–9, _)
\w+
“hello123”
\s
Any whitespace
\s
“ ”, “	”
`
`
OR
`cat
()
Group
(ab)+
“abab”
Examples
1. Search for a Word
import re
text = "Python is powerful"
match = re.search("powerful", text)
if match:
    print("Found:", match.group())
Output:
Found: powerful
2. Check if String Starts with “Hello”
import re
text = "Hello World"
if re.match("^Hello", text):
    print("Starts with Hello")
Output:
Starts with Hello
3. Find All Numbers
import re
text = "Order numbers: 123, 456, and 789"
numbers = re.findall(r"\d+", text)
print(numbers)
Output:
['123', '456', '789']
4. Replace Text
import re
text = "I love Java"
result = re.sub("Java", "Python", text)
print(result)
Output:
I love Python
5. Split by Non-Alphabetic Characters
import re
text = "apple,banana;orange|grape"
fruits = re.split(r"[,;|]", text)
print(fruits)
Output:
['apple', 'banana', 'orange', 'grape']
6. Validate Email Example
import re
email = "user.name@example.com"
pattern = r"^[\w\.-]+@[\w\.-]+\.\w+$"
if re.match(pattern, email):
    print("Valid email")
else:
    print("Invalid email")
Output:
Valid email
Match Object Details
If a match is found using re.search() or re.match(), it returns a
match object.
Example:
import re
text = "My number is 9876543210"
match = re.search(r"\d+", text)
if match:
    print("Matched text:", match.group())
    print("Start index:", match.start())
    print("End index:", match.end())
Output:
Matched text: 9876543210
Start index: 13
End index: 23
Summary
Use Case
Function
Example
Find a word
re.search()
re.search("word", text)
Find all matches
re.findall()
re.findall(r"\d+", text)
Replace text
re.sub()
re.sub("old", "new", text)
Split text
re.split()
re.split(r"\s+", text)
Validate pattern
re.match()
re.match(r"^[A-Za-z]+$", text)

Function	Description
`re.match()`	Matches pattern only at the beginning of a string
`re.search()`	Searches for a pattern anywhere in the string
`re.findall()`	Returns all matches in a list
`re.finditer()`	Returns iterator of match objects
`re.sub()`	Replaces matches with another string
`re.split()`	Splits a string by the pattern

Use Case	Function	Example
Find a word	`re.search()`	`re.search("word", text)`
Find all matches	`re.findall()`	`re.findall(r"\d+", text)`
Replace text	`re.sub()`	`re.sub("old", "new", text)`
Split text	`re.split()`	`re.split(r"\s+", text)`
Validate pattern	`re.match()`	`re.match(r"^[A-Za-z]+$", text)`

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Explain the Python RegEx with Example

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2 Answers

What is RegEx?

Common RegEx Functions in Python (`re` module)

Basic Syntax

Examples

1. Search for a Word

2. Check if String Starts with “Hello”

3. Find All Numbers

4. Replace Text

5. Split by Non-Alphabetic Characters

6. Validate Email Example

Match Object Details

Summary

Liked By

Symbol	Meaning	Example	Matches
`.`	Any character (except newline)	`a.c`	“abc”, “axc”
`^`	Start of string	`^Hello`	“Hello world”
`$`	End of string	`world$`	“Hello world”
`*`	0 or more repetitions	`go*d`	“gd”, “god”, “good”
`+`	1 or more repetitions	`go+d`	“god”, “good”
`?`	0 or 1 repetition	`go?d`	“gd”, “god”
`{n}`	Exactly n times	`\d{3}`	“123”
`{n,m}`	Between n and m times	`\d{2,4}`	“12”, “1234”
`[]`	Any one of listed characters	`[aeiou]`	Any vowel
`\d`	Any digit	`\d`	“0–9”
`\w`	Any word char (a–z, A–Z, 0–9, _)	`\w+`	“hello123”
`\s`	Any whitespace	`\s`	“ ”, “\t”
`	`	OR	`cat
`()`	Group	`(ab)+`	“abab”