🟡 Advanced Python · Lesson 23

Regular Expressions with re Module

re Module के साथ Regular Expressions

What is Regular Expressions?

Regular Expressions means regular expressions search, match and validate text patterns such as email, phone number and roll number formats.

In real programs, this topic helps in validating email/mobile/roll number. Learn the idea first, then type the program yourself and compare the output.

💡 At a Glance

Point	Details
Course Area	Advanced Python Professional concepts used to make code reusable, clean and project-ready.
Main Use	validating email/mobile/roll number
Example File	`regular-expressions.py`
Practice Focus	Run, change values, and explain the output line by line.

Why should you learn this?

It is useful for validating email/mobile/roll number.
It connects with extracting patterns from text.
It improves your ability to read, write and debug Python programs.

Important Terms

These terms are used directly in this lesson. Understand them before memorising the code.

Term	Meaning
re module	Python module used for regular expressions.
pattern	Special text rule used to search or validate data.
match	Checking whether text satisfies a pattern.
search	Finding a pattern anywhere in text.
validation	Checking whether data follows the required format.

Syntax / Basic Pattern

The simple pattern is: prepare data, apply the concept, then show the result.

Basic Pattern

import re
text = "Contact: student@example.com"
pattern = r"[\w.-]+@[\w.-]+\.\w+"
match = re.search(pattern, text)
if match:
    print("Email found:", match.group())

Complete Example Program

Python – regular-expressions.py

import re

text = "Contact: student@example.com"
pattern = r"[\w.-]+@[\w.-]+\.\w+"

match = re.search(pattern, text)
if match:
    print("Email found:", match.group())

Expected Output

Email found: student@example.com

Program Explanation

import re imports ready-made features from a module/library.
text = "Contact: student@example.com" stores a value in text.
pattern = r"[\w.-]+@[\w.-]+\.\w+" stores a value in pattern.
match = re.search(pattern, text) stores a value in match.
if match: checks a condition and runs the indented block when it is true.
print("Email found:", match.group()) displays information or calculated result on the screen.

Where will you use it?

Validating email/mobile/roll number.
Extracting patterns from text.
Cleaning imported data.

Common Mistakes

Making code complex when a simple function or class is enough.
Not handling possible errors or edge cases.
Mixing project dependencies instead of using a virtual environment.

Practice Tasks

Type the program in regular-expressions.py and run it.
Change input values or sample data and observe the new output.
Create one example related to validating email/mobile/roll number.
Write 5 lines explaining the logic in your own words.

Summary

Regular Expressions is not a theory-only topic. You should be able to explain the meaning, write the example, run it successfully, and use it in a small practical program.

Regular Expressions क्या है?

Regular Expressions ka matlab hai: Regular expressions search, match and validate text patterns such as email, phone number and roll number formats. Simple words me, ye topic practical Python programs likhne me direct use hota hai.

Is topic ko sirf definition ke liye nahi, balki validating email/mobile/roll number jaise real examples ke liye practice karein.

यह क्यों सीखना जरूरी है?

Ye validating email/mobile/roll number me kaam aata hai.
Ye extracting patterns from text se bhi connected hai.
Isse aap code ka output aur errors better samajh paate hain.

Important Terms

Term	Meaning
re module	Python module used for regular expressions.
pattern	Special text rule used to search or validate data.
match	Checking whether text satisfies a pattern.
search	Finding a pattern anywhere in text.
validation	Checking whether data follows the required format.

Syntax / Basic Pattern

Basic idea: pehle data तैयार करें, phir Python logic apply करें, aur finally result display करें.

Basic Pattern

import re
text = "Contact: student@example.com"
pattern = r"[\w.-]+@[\w.-]+\.\w+"
match = re.search(pattern, text)
if match:
    print("Email found:", match.group())

Complete Example Program

Python – regular-expressions.py

import re

text = "Contact: student@example.com"
pattern = r"[\w.-]+@[\w.-]+\.\w+"

match = re.search(pattern, text)
if match:
    print("Email found:", match.group())

Expected Output

Email found: student@example.com

Program Explanation

import re imports ready-made features from a module/library.
text = "Contact: student@example.com" stores a value in text.
pattern = r"[\w.-]+@[\w.-]+\.\w+" stores a value in pattern.
match = re.search(pattern, text) stores a value in match.
if match: checks a condition and runs the indented block when it is true.
print("Email found:", match.group()) displays information or calculated result on the screen.

Practical Uses

Validating email/mobile/roll number.
Extracting patterns from text.
Cleaning imported data.

Common Mistakes

Making code complex when a simple function or class is enough.
Not handling possible errors or edge cases.
Mixing project dependencies instead of using a virtual environment.

Practice Tasks

Program ko regular-expressions.py file me type karke run karein.
Values change karke output compare karein.
validating email/mobile/roll number par ek छोटा example banayen.
Logic ko apne words me 5 lines me likhein.

सारांश

Regular Expressions ko tab complete maanenge jab aap iska meaning, example, output aur practical use clearly explain kar saken.

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