Comparison operators — ==, !=, - , - , - =, - =

1.2.7 · Coding › Introduction to Programming (Python)

YEH HAIN KYA

Definition Comparison (relational) operators

Aisi operators jo do operands ko compare karti hain aur ek Boolean (True/False) return karti hain.

Operator	Padha jaata hai	`True` tab jab…
`==`	equal to	dono sides ki value same ho
`!=`	not equal to	sides alag hon
`<`	less than	left wala chota ho
`>`	greater than	left wala bada ho
`<=`	less than or equal	left ≤ right
`>=`	greater than or equal	left ≥ right

Common mistake

= aur == ek NAHI hain Galat idea kyun sahi lagta hai: Maths mein, = ka matlab "equals" hota hai. Toh x = 5 dikha jaisa ek sawaal "kya x paanch hai?". Sachai: Python mein = assignment hai (5 ko x mein daalo). Sawaal "kya x paanch hai?" x == 5 se hota hai. Fix: Ek = ek variable ko badalta hai; do == ek variable ko check karta hai.

x = 5      # assignment: store 5
x == 5     # comparison: True

Bonus: if x = 5: ek SyntaxError raise karta hai, jo Python ka tumhari madad karne ka tarika hai.

JAWAB KAISE BANTA HAI (first principles se derivation)

Comparison koi jaadu nahi hai — yeh ek fundamental idea tak reduce hoti hai: values ki ordering / identity.

Step 1 — humein asli mein sirf ek primitive chahiye: < (less-than). Kyun? Kyunki har doosri comparison ko < plus logical NOT aur equality se define kiya ja sakta hai:

a > b a \leq b a \geq b a == b a \neq = b \equiv b < a \equiv \neg (b < a) \equiv \neg (a < b) \equiv \neg (a < b) \land \neg (b < a) \equiv \neg (a == b)

Yeh step kyun? Agar na a < b true hai na b < a, toh dono values ko alag order nahi kiya ja sakta — matlab woh equal hone chahiye. Isi tarah ek sort algorithm, sirf < jaante hue bhi, bata sakti hai ki cheezein equal hain.

Step 2 — har operator ek Boolean return karta hai, aur Python Booleans secretly integers hain:

$True = 1, False = 0$

Yeh kyun matter karta hai: True + True == 2 valid Python hai. Toh sum(x > 0 for x in data) literally count karta hai ki kitne items positive hain — comparisons counters ban jaati hain.

Worked examples

Worked example 1 — Numbers

print(7 == 7.0)   # True
print(7 != 8)     # True
print(3 <= 3)     # True
print(3 < 3)      # False

7 == 7.0 True kyun hai? == value compare karta hai, type nahi. Python pehle int 7 ko float 7.0 mein widen karta hai, phir equality check karta hai.

Worked example 2 — Strings lexicographically compare hoti hain (dictionary order)

print("apple" < "banana")  # True
print("Zebra" < "apple")   # True  (!)

"Zebra" < "apple" kyun? Strings character by character Unicode/ASCII code points use karke compare hoti hain. 'Z' 90 hai, 'a' 97 hai. Kyunki 90 < 97, uppercase jeet jaata hai. Lesson: casing ordering ko affect karta hai — names compare karne se pehle .lower() lagao.

Worked example 3 — Comparisons se counting

scores = [85, 40, 92, 55, 30]
passed = sum(s >= 50 for s in scores)   # 3

Yeh step kyun? Har s >= 50 ya to True(=1) hai ya False(=0); sum 1s ko jodhta hai. Koi if nahi chahiye — comparisons hi counter hain.

Worked example 4 — Range check ke liye chaining

age = 25
if 18 <= age <= 60:
    print("eligible")

Yeh step kyun? Bilkul "18 ≤ age ≤ 60" jaisa padhta hai aur age ko ek baar evaluate karta hai. age >= 18 and age <= 60 se zyaada clean hai.

Figure — Comparison operators — ==, !=, - , - , - =, - =

Common mistake Floating-point

== ek trap hai Galat idea kyun sahi lagta hai: 0.1 + 0.2 hona chahiye 0.3, toh 0.1 + 0.2 == 0.3 hona chahiye True. Sachai: Yeh False hai. Binary 0.1 ko exactly store nahi kar sakti, toh sum 0.30000000000000004 ban jaata hai. Fix: Tolerance ke saath compare karo:

abs((0.1 + 0.2) - 0.3) < 1e-9   # True

Common mistake

== vs is Galat idea kyun sahi lagta hai: Dono "same" jaise lagte hain. Sachai: == equal value check karta hai; is memory mein same object check karta hai.

a = [1, 2]; b = [1, 2]
a == b   # True  (same contents)
a is b   # False (different objects)

Fix: Values ke liye == use karo; is sirf None ke liye rakhho (x is None).

Forecast-then-Verify

Recall Output predict karo PEHLE aage padhne se

print(5 > 3 > 1)
print("b" == "B")
print(True + (2 == 2))
print(1 == 1.0 == 1)

Answers: True (5>3 aur 3>1) · False (case alag hai) · 2 (1 + True=1) · True (chained, sab equal).

Active recall

Ek comparison operator hamesha kya return karta hai?

Ek Boolean — True ya False.

= aur == mein kya fark hai?

= ek value assign karta hai; == equality test karta hai.

7 == 7.0 True kyun hai?

== value compare karta hai, type nahi; int ko float mein widen kiya jaata hai.

Python mein a < b < c kya expand hota hai?

(a < b) and (b < c), jisme b ek baar evaluate hota hai.

0.1 + 0.2 == 0.3 False kyun hai?

Floating-point rounding ki wajah se; sum 0.30000000000000004 ban jaata hai.

Floats ko safely kaise compare karte hain?

abs(x - y) < tiny_tolerance check karo.

== aur is mein kya fark hai?

== = equal value; is = same object identity.

True aur False kis integer value ke barabar hain?

True = 1, False = 0.

"Zebra" < "apple" True kyun hai?

Uppercase letters ke ASCII codes lowercase se chote hote hain.

sum(x > 0 for x in data) positives kaise count karta hai?

Har comparison 1 ya 0 hai; sum 1s ko jodhta hai.

Recall Feynman: 12-saal ke bachche ko samjhao

Ek referee imagine karo jo sirf haan ya naa mein hi jawab deta hai. Tum referee ko do cheezein aur ek sawaal dete ho: "Kya yeh bada hai?" "Kya yeh same hain?" Referee kabhi lamba jawab nahi deta — bas ek thumbs up (True) ya thumbs down (False). Tumhara program phir thumb ke hisaab se alag-alag kaam karta hai. Bas itna hi ek comparison operator hai: ek chota sa haan/naa referee. Aur yahan ek raaz hai — thumbs up secretly 1 count hota hai aur thumbs down 0, toh agar tum bahut saare thumbs-up ko jodhao tum count kar sakte ho ki kitni baar "haan" hua!

Connections

Boolean values and type bool — har comparison ka output type
Logical operators — and, or, not — comparisons ko bade conditions mein combine karo
if-elif-else statements — comparisons har branch chalate hain
while loops — loop condition ek comparison hai
Floating point representation — == float trap explain karta hai
ASCII and Unicode — string ordering explain karta hai
Identity vs equality (is vs ==) — is/== ki gehri kahani