Python Regex Tutorial for Beginners

2. What Is Regex in Python?

import re

text = "Python Regex Tutorial"

result = re.match("Python", text)

print(result)

import re

text = "Learn Python Regex"

result = re.search("Regex", text)

print(result)

Output

import re

text = "Order 1001, Order 1002, Order 1003"

numbers = re.findall(r"\d+", text)

print(numbers)

Output

• \d → Digit (0–9)
• + → One or more occurrences

import re

text = "Price: $100"

result = re.sub(r"\d+", "200", text)

print(result)

Output

II. Alphabets ([a-z] and [A-Z])

III. Word Characters (\w)

import re

email = "john.doe@gmail.com"

pattern = r'^[\w\.-]+@[\w\.-]+\.\w+$'

if re.match(pattern, email):

    print("Valid Email")

else:

    print("Invalid Email")

Output

Valid Email

Explanation

Let's understand how this Python Regex email validation pattern works step by step.

Note: The r before the pattern is called a raw string prefix. It tells Python not to treat backslashes (\) as special escape characters. This is useful in Regex because patterns often contain backslashes such as \w, \d, and \s. Using r allows us to write the Regex pattern exactly as intended without adding extra backslashes.

r'^[\w\.-]+@[\w\.-]+\.\w+$'

a) ^[\w\.-]+

Here:

• \w matches letters, numbers, and underscores
• \. matches a literal dot (.)
• - matches a hyphen (-)
• + means one or more of the allowed characters
• ^ ensures matching starts from the beginning of the string

The backslash (\) is called an escape character in Regex. It either gives special meaning to a character (such as \w) or removes the special meaning of a character (such as \. to match an actual dot).

b) @

This part checks for the presence of the @ symbol, which separates the username from the domain name.

Example:

john.doe@gmail.com

Every valid email address must contain exactly one @ symbol.

c) [\w\.-]+

This section validates the domain name.

Examples:

• gmail
• outlook
• company-name

It allows letters, numbers, dots, and hyphens inside the domain portion.

d) \.\w+$

This part validates the domain extension.

Examples:

• .com
• .org
• .net
• .edu

The \. matches the actual dot before the extension, while \w+ checks that the extension contains one or more characters.

The $ symbol ensures that matching ends at the end of the string.

How the Validation Works

Consider the email:

john.doe@gmail.com

Regex checks:

Since all required parts are present, the email is considered valid.

import re

password = "Python2026"

pattern = r'^(?=.*[a-z])(?=.*[A-Z])(?=.*\d).{8,}$'

if re.match(pattern, password):
    print("Strong Password")
else:
    print("Weak Password")

import re

phone = "9876543210"

pattern = r'^\d{10}$'

if re.match(pattern, phone):
    print("Valid Phone Number")
else:
    print("Invalid Phone Number")

Why Phone Number Validation Matters

• OTP verification systems
• Banking and financial applications
• E-commerce platforms
• Food delivery applications
• Ride-sharing services
• Customer registration portals
• Healthcare appointment systems

I. Extracting Order IDs from Application Logs

re.search("python", text)

Better

"python" in text

re.search(pattern, text)

Use

compiled = re.compile(pattern)

compiled.search(text)

re.search("python", text)

"python" in text

import re

email_pattern = r'^[\w\.-]+@company\.com$'
username_pattern = r'^[A-Za-z0-9_]{4,20}$'
employee_pattern = r'^EMP-\d{5}$'
password_pattern = r'^(?=.*[a-z])(?=.*[A-Z])(?=.*\d).{8,}$'

email = "john@company.com"
username = "john_admin"
employee_id = "EMP-12345"
password = "SecurePass2026"

print(bool(re.match(email_pattern, email)))
print(bool(re.match(username_pattern, username)))
print(bool(re.match(employee_pattern, employee_id)))
print(bool(re.match(password_pattern, password)))