Python me Sets kya hote hain?

Set Python ka ek unordered collection hai jisme duplicate values nahi hoti. Matlab agar aap same value baar baar daalo, woh sirf ek baar store hogi. Set ka use mainly unique items store karne aur mathematical set operations (union, intersection, difference) ke liye hota hai.

Set ki 4 main khasiyatein hain :-

Unordered — items ka koi fixed order nahi hota
No Duplicates — same value sirf ek baar store hogi
Mutable — items add ya remove ho sakte hain
Not Indexed — index se access nahi kar sakte (s[0] nahi chalega)

Is page me yeh sab sikhenge :-

1. Set banana aur basics
2. Items add aur remove karna
3. Set Operations — union, intersection, difference, symmetric difference
4. Set Methods — subset, superset, disjoint
5. Set Comprehension
6. Frozen Set

1. Set Banana aur Basics

Set ko curly brackets { } me likha jaata hai. Note: Empty set banane ke liye set() likhna padta hai — sirf { } likhne se empty dictionary ban jaati hai!

Example 1: Set banana — duplicates automatic remove ho jaate hain

Python

In [1]:

nums = {1, 2, 3, 2, 1, 4, 3, 5}   # duplicates hain
print("Set:", nums)                # duplicates auto remove!
print("Type:", type(nums))
print("Length:", len(nums))

# Empty set banana
empty_set = set()
print("Empty set:", empty_set)

Output

Example 2: List se duplicates hatane ke liye set use karna

Python

In [1]:

votes = ["Delhi", "Mumbai", "Delhi", "Chennai", "Mumbai", "Delhi"]
print("Original list:", votes)
print("Total votes:", len(votes))

# Set se unique cities nikalo
unique_cities = set(votes)
print("Unique cities:", unique_cities)
print("Unique count:", len(unique_cities))

# Wapas list me convert
unique_list = list(unique_cities)
print("As list:", unique_list)

Output

Example 3: Set indexed nahi hota — in operator se check karo

Python

In [1]:

fruits = {"apple", "mango", "banana", "grapes"}

# in operator se membership check karo
print("apple in fruits:", "apple" in fruits)
print("pizza in fruits:", "pizza" in fruits)

# Index se access nahi kar sakte — error aayega
try:
    print(fruits[0])
except TypeError as e:
    print("Error:", e)

Output

2. Items Add aur Remove Karna

Set me items add() aur update() se add hote hain, aur remove(), discard(), pop() se remove hote hain.

Method	Kaam
add(x)	Ek item add karta hai
update(iterable)	Multiple items add karta hai
remove(x)	Item remove — nahi mila toh KeyError
discard(x)	Item remove — nahi mila toh koi error nahi
pop()	Koi bhi ek random item remove karke return
clear()	Saare items hata deta hai

Example 1: add() aur update()

Python

In [1]:

languages = {"Python", "Java"}
print("Before:", languages)

languages.add("C++")
print("After add:", languages)

languages.update(["Go", "Rust", "Python"])  # Python duplicate nahi hoga
print("After update:", languages)

Output

Example 2: remove() vs discard() — fark samjho

Python

In [1]:

s = {"apple", "banana", "mango"}

s.remove("banana")          # exists — theek se remove
print("After remove:", s)

s.discard("grapes")         # exist nahi karta — phir bhi error nahi!
print("After discard (grapes):", s)

# remove karo jo exist nahi karta — KeyError
try:
    s.remove("grapes")
except KeyError as e:
    print("remove() Error:", e)

Output

Example 3: pop() aur clear()

Python

In [1]:

s = {10, 20, 30, 40, 50}
print("Original:", s)

popped = s.pop()   # random item remove hoga
print("Popped item:", popped)
print("After pop:", s)

s.clear()
print("After clear:", s)

Output

3. Set Operations

Set ka sabse powerful feature hai mathematical operations. Ye operations operators se bhi ho sakti hain aur methods se bhi.

Operation	Operator	Method	Matlab
Union	a \| b	a.union(b)	Dono sets ke saare items
Intersection	a & b	a.intersection(b)	Sirf common items
Difference	a - b	a.difference(b)	a me jo b me nahi
Symmetric Diff	a ^ b	a.symmetric_difference(b)	Dono me exclusive items

Example 1: Union (|) aur Intersection (&)

Python

In [1]:

maths   = {"Rahul", "Priya", "Arjun", "Neha"}
science = {"Priya", "Vikram", "Neha", "Sana"}

# Union — dono classes ke saare students
all_students = maths | science
print("Union (|):", all_students)

# Intersection — dono classes me common students
both = maths & science
print("Intersection (&):", both)

Output

Example 2: Difference (-) aur Symmetric Difference (^)

Python

In [1]:

a = {1, 2, 3, 4, 5}
b = {3, 4, 5, 6, 7}

# Difference — a me jo b me nahi hain
print("a - b:", a - b)   # {1, 2}
print("b - a:", b - a)   # {6, 7}

# Symmetric Difference — jo sirf ek me hain
print("a ^ b:", a ^ b)   # {1, 2, 6, 7}

Output

Example 3: Real-life — do websites ke common visitors

Python

In [1]:

site_A = {"user1", "user2", "user3", "user4", "user5"}
site_B = {"user3", "user4", "user5", "user6", "user7"}

print("Dono pe aaye   :", site_A & site_B)
print("Sirf A pe aaye :", site_A - site_B)
print("Sirf B pe aaye :", site_B - site_A)
print("Total unique   :", site_A | site_B)

Output

4. Set Methods — Subset, Superset aur In-place Operations

Set ke kuch aur useful methods hain — check karne ke liye ki ek set doosre ka subset ya superset hai, aur in-place update ke liye.

Example 1: issubset(), issuperset(), isdisjoint()

Python

In [1]:

all_students = {"Rahul", "Priya", "Arjun", "Neha", "Vikram"}
top_students = {"Priya", "Arjun"}
other_class  = {"Riya", "Amit"}

# issubset — kya top_students, all_students ka hissa hai?
print("top subset of all?   :", top_students.issubset(all_students))

# issuperset — kya all_students top ko cover karta hai?
print("all superset of top? :", all_students.issuperset(top_students))

# isdisjoint — kya dono me koi common item nahi?
print("all & other disjoint?:", all_students.isdisjoint(other_class))

Output

Example 2: intersection_update() aur difference_update()

Python

In [1]:

a = {1, 2, 3, 4, 5}
b = {3, 4, 5, 6, 7}

# intersection_update — a ko sirf common items tak ghata do (in-place)
a.intersection_update(b)
print("After intersection_update:", a)   # {3, 4, 5}

x = {1, 2, 3, 4, 5}
y = {3, 4}
# difference_update — x se y ke items hata do (in-place)
x.difference_update(y)
print("After difference_update:", x)     # {1, 2, 5}

Output

5. Set Comprehension

List comprehension ki tarah Set Comprehension bhi hoti hai — ek line me set banana with conditions. Automatically duplicates remove ho jaate hain.

Example 1: Squares ka set — duplicates hatenge automatically

Python

In [1]:

nums = [-3, -2, -1, 0, 1, 2, 3]

# -2 aur 2 dono ka square 4 hai — sirf ek store hoga
squares = {n ** 2 for n in nums}
print("Squares set:", squares)

# Sirf even squares
even_sq = {n**2 for n in range(1, 11) if n % 2 == 0}
print("Even squares:", even_sq)

Output

Example 2: Sentence se unique words nikalna

Python

In [1]:

sentence = "to be or not to be that is the question to be"

unique_words = {word for word in sentence.split()}
print("Unique words:", unique_words)
print("Total unique:", len(unique_words))

Output

6. Frozen Set

frozenset ek immutable set hai — yaani ek baar banane ke baad isme koi change nahi ho sakta. Yeh bilkul waise hai jaise tuple, list ka immutable version hota hai. frozenset ko dictionary key ke roop me bhi use kar sakte hain (normal set nahi).

Example 1: frozenset banana aur use karna

Python

In [1]:

fs = frozenset([1, 2, 3, 4, 5])
print("Frozenset:", fs)
print("Type:", type(fs))

# Membership check chal sakta hai
print("3 in fs:", 3 in fs)
print("Length:", len(fs))

# Lekin add ya remove nahi kar sakte
try:
    fs.add(6)
except AttributeError as e:
    print("Error:", e)

Output

Example 2: frozenset pe set operations bhi chal sakti hain

Python

In [1]:

fa = frozenset([1, 2, 3, 4])
fb = frozenset([3, 4, 5, 6])

print("Union       :", fa | fb)
print("Intersection:", fa & fb)
print("Difference  :", fa - fb)

# frozenset as dictionary key — ye normal set nahi kar sakta!
d = {fa: "Group A", fb: "Group B"}
print("Dict:", d)

Output

Quick Summary — Set ek nazar me

Concept	Kaam	Example
Banana	{ } me items	s = {1, 2, 3}
Empty set	set() use karo	s = set()
add(x)	Ek item add	s.add(5)
update()	Multiple add	s.update([4,5])
remove(x)	Hatao — error if missing	s.remove(3)
discard(x)	Hatao — no error	s.discard(3)
Union (\|)	Saare items	a \| b
Intersection (&)	Common items	a & b
Difference (-)	a me jo b me nahi	a - b
Sym. Diff (^)	Exclusive items	a ^ b
issubset()	Subset check	a.issubset(b)
issuperset()	Superset check	a.issuperset(b)
isdisjoint()	Koi common nahi?	a.isdisjoint(b)
frozenset	Immutable set	frozenset([1,2,3])

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