Python Variables & Data Types

What is a variable?

A variable is a name bound to a value. Python me variable create karne ke liye separate type declaration required nahi hoti.

name = "Broun"
age = 21
is_learning = True

print(name)
print(age)
print(is_learning)

Try it Yourself →

Assignment with =

= is the assignment operator. It does not mean mathematical equality.

score = 70
score = 85

print(score)

Output 85 hoga because second assignment name ko new value se bind karta hai.

Variable naming rules

• Name letters ya underscore se start ho sakta hai.
• Digits name me aa sakte hain, but first character nahi ho sakte.
• Spaces allowed nahi hain.
• Python keywords variable names nahi ho sakte.
• Names case-sensitive hote hain.

student_name = "Aman"
chapter2_score = 92
_private_value = "internal"

print(student_name, chapter2_score)

Choose meaningful names

# Weak
x = 1200

# Clearer
monthly_fee = 1200

Short names small formulas/loops me useful ho sakte hain, but business data ke liye intent clear rakhna better hai.

Check a value with type()

type() value ka runtime type object return karta hai.

print(type(10))
print(type(3.5))
print(type("Python"))
print(type(True))
print(type(None))

Run type() examples →

Integer: int

int whole numbers represent karta hai.

students = 45
balance = -250
zero = 0

print(type(students))

Python integers arbitrary precision support karte hain, so fixed 32-bit/64-bit limit jaisi restriction normal Python int par directly apply nahi hoti; available memory practical limit hoti hai.

Decimal numbers: float

float floating-point numbers represent karta hai.

price = 199.99
temperature = -2.5

print(price)
print(type(price))

Complex numbers: complex

Python built-in complex type bhi provide karta hai. Imaginary part ke liye j notation use hota hai.

value = 2 + 3j
print(value)
print(type(value))

Beginner everyday applications me complex numbers less common hain, but built-in numeric type ke roop me jaana useful hai.

Text: str

Python text ko str type me represent karta hai. Single, double aur triple-quoted literals different situations me useful ho sakte hain.

course = "Python"
message = 'Learn by practice'
multiline = """Line one
Line two"""

print(course)
print(message)
print(multiline)

Strings ko Chapter 8 me indexing, slicing, methods aur formatting ke saath detail me padhenge.

Boolean: bool

bool ke two values hain: True and False.

is_logged_in = True
has_completed = False

print(type(is_logged_in))

Capital T aur F required hain; true/false Python boolean literals nahi hain.

None and NoneType

None absence of a value ko represent karne ke liye commonly use hota hai.

selected_course = None

print(selected_course)
print(type(selected_course))

None empty string, zero ya False ke same nahi hai.

Python is dynamically typed

Name ka type permanently declare nahi hota. Same name different times par different types ke values se bind ho sakta hai.

value = 10
print(type(value))

value = "ten"
print(type(value))

Multiple assignment

Python ek line me multiple names bind kar sakta hai.

name, age, active = "Aman", 22, True
print(name, age, active)

Values ki count names ki count se match honi chahiye, unless advanced unpacking syntax intentionally use ho.

Assign the same value to multiple names

a = b = c = 0
print(a, b, c)

Immutable numbers ke case me simple hai. Mutable objects ke saath chained assignment later important reference-sharing behavior create kar sakta hai.

Names refer to objects

Python variables ko beginner-friendly shorthand me “boxes” kehna useful ho sakta hai, but technically names objects ko reference karte hain.

first = "Python"
second = first

print(first)
print(second)

Mutable objects ke references ka practical effect lists/dictionaries chapters me clear hoga.

Constants are a convention

Python me normal variable ko JavaScript const jaisa enforce karne wala general keyword nahi hai. Uppercase naming convention constant intent signal karti hai.

MAX_ATTEMPTS = 3
APP_NAME = "BrounStack"

Uppercase name runtime reassignment ko prevent nahi karta; it is a convention.

Delete a name with del

del current namespace se name binding remove kar sakta hai.

temporary = "remove me"
print(temporary)

del temporary
# print(temporary)  # NameError

Normal code me variables ko manually delete karna frequently necessary nahi hota.

Mutable vs immutable preview

Some Python objects can be changed in place and some cannot. This distinction later lists, dictionaries, sets aur function behavior me important hoga.

• Common immutable examples: int, float, bool, str, tuple.
• Common mutable examples: list, dict, set.

Common beginner mistakes

• 1name jaisa identifier use karna.
• Variable name me spaces rakhna.
• Keyword jaise class ko variable banana.
• True/False ki capitalization galat karna.
• = ko comparison operator samajhna.
• None ko empty string ya zero samajhna.
• Variable type ko permanently fixed assume karna.
• Float ko exact decimal arithmetic samajhna.
• Meaningless names everywhere use karna.
• Uppercase constant convention ko runtime protection samajhna.

Beginner best practices

• Descriptive snake_case names use karo.
• Same variable ka meaning stable rakho.
• Expected type confirm karne ke liye learning/debugging me type() use karo.
• Boolean names ko is_, has_, can_ jaise prefixes se readable banao where appropriate.
• None ko explicit “no value yet” state ke liye intentionally use karo.
• Examples edit karke different values test karo.

Chapter checklist

• Variable aur assignment ka difference samajh aaya?
• Valid Python naming rules yaad hain?
• int, float, complex, str, bool aur None identify kar sakte ho?
• type() use kar sakte ho?
• Dynamic typing ka basic meaning clear hai?
• Multiple assignment samajh aaya?
• Constant uppercase convention aur actual enforcement ka difference clear hai?
• Mutable vs immutable ka preview samajh aaya?

Open practice starter →