Lesson 02 � Foundation

VALUE KO
NAAM DO.

Variable ko labelled box kehna useful start hai, lekin complete picture nahi. Python mein variable ek naam hai jo kisi value ko refer karta hai. Naam badalta nahi; jis value ki taraf woh point kar raha hai, woh badal sakti hai.

? 18 min✓ BeginnerPrerequisite: print()

WHY: hard-code kyun nahi?

Socho aap ek student report bana rahe ho. Agar har jagah "Aman" aur 92 likhoge, student change hote hi poora code search karke edit karna padega. Variable se value ek jagah define hoti hai, aur baaki code meaningful naam use karta hai.

WHAT

Assignment operator = right-side ki value ko left-side ke variable name se bind karta hai.

WHEN

Jab data later change ho sakta ho: name, price, score, API response ya user input.

RULE

Variable name letter ya underscore se start hota hai; spaces aur hyphens allowed nahi hote.

HOW: assignment ko left se right padho

student_name = "Aman"
score = 92

print(student_name)
print(score)

Yahan student_name mein text value aur score mein number value hai. Python variable ka type separately declare karne ko nahi bolta; value se infer karta hai.

ℹ

= equality check nahi hai. Is line ka matlab �score is equal to 92� compare karna nahi; matlab �score naam ko ab 92 se jod do� hai. Equality check ke liye later == use hota hai.

Reassignment: value update ho sakti hai

Variable ko dobara assign karoge to naam new value ko point karega. Is pattern se counter, total aur user state banti hai.

cart_total = 499
cart_total = cart_total + 200

print(cart_total) # 699

Right-side calculation pehle hoti hai. Phir new result cart_total ko reassign hota hai. Yeh line cart_total = cart_total + 200 maths equation nahi hai�program state update hai.

Readable names = future-you ki help

Good: monthly_revenue, is_logged_in, student_count
Avoid: x, data1, my variable
Convention: Python mein snake_case common hai�words ko underscore se jodo.
Reserved words: class, for, if ko variable name nahi bana sakte.

Try it: mini profileValues ko apna bana ke run karo

main.pyOptional input

Code ko apni info se update karke run karein

Quick check

Ek variable city banao jisme text Lucknow store ho. Answer lowercase mein check hoga.

Text value quotes ke andar hogi. Left mein variable name, beech mein =.

Common mistakes

student name = "Aman" invalid hai; space ki jagah student_name use karein.
2score = 90 invalid hai; name digit se start nahi hota.
Score aur score different variables hain�Python case-sensitive hai.
Variable ko list ya str naam dena future mein built-in tools ko hide kar sakta hai.

Variables clear?

Ab same variable ke andar kis kind ki values�text, number, boolean�aa sakti hain, woh samjho.

VALUE KONAAM DO.