for Loop aur range() (Seedhi Dar Seedhi Ginti!)
range() ke teen roop, ulti ginti, chhalaang wali ginti aur for loop ka poora safar, step-by-step 🔢🐍
🧭 Is Post Mein
📖 Kahani: Golu ki Chhalaang Wali Seedhiyan
Recess khatam hone wali thi. Computer lab upar thi, aur school ki seedhi mein 20 seedhiyan thi. Golu jaldi mein tha, toh woh ek seedhi chhod kar chadhne laga: 2, 4, 6, 8…
Priya neeche se gin rahi thi: “Golu ne pair rakha seedhi 2, 4, 6, 8, 10, 12, 14, 16, 18 aur 20 par. Kul 10 baar pair rakha!” Rohan hansa: “Aur main toh har seedhi par chadhta hoon: 1, 2, 3… 20. Mere 20 kadam!”
Lab mein pahunch kar Priya ne laptop khola: “Pichli baar humne range(5) dekha tha. Par range sirf 0 se ginti nahi karta. Usse hum kahan se shuru, kahan ruko aur kitni chhalaang, teeno bata sakte hain!” Usne likha range(2, 21, 2), aur screen par aaya: 2 4 6 8 10 12 14 16 18 20. Bilkul Golu ke kadam! 😲
Golu chakra gaya: “Par 21 kyun likha? Seedhiyan toh 20 hi hain!” Aur Rohan ne poochha: “Neeche utarte waqt ulti ginti kaise karein?” Chaliye, aaj range() ka poora raaz kholte hain. 🔢
🎯 Is Post Mein Kya Seekhenge
- for loop ka poora syntax: for variable in sequence: aur har shabd ka matlab
- range() function ke teen roop: range(stop), range(start, stop), range(start, stop, step)
- Stop shaamil kyun nahi hota (Golu ka “21 kyun?” wala sawaal)
- Ulti ginti (negative step) aur khaali range (jab loop ek baar bhi na chale)
- range ki values ginna aur dekhna: list() aur len() ki madad se
- for loop chalne ka step-by-step safar, trace table ke saath, aur print(…, end=” “) se ek line mein output
- range ki aam galtiyan: step 0 (ValueError) aur dashamlav number (TypeError)
🧱 Basics: Pehle Yeh Aana Chahiye
1. Loop: instructions ko baar-baar chalane ka tareeka. Loop ke ek chakkar ko iteration kehte hain. (Pichle post Loop Kya Hai? mein detail hai.)
2. Colon aur indentation: for wali line ke aakhir mein colon ( : ), aur body ki lines 4 space andar. Python body ko indentation se hi pehchaanta hai.
3. Variable: naam wala dibba. Loop mein ek variable (jaise i) har chakkar mein nayi value pakadta hai.
4. Integer (poora number): 0, 5, -3, 100 jaise number jinmein dashamlav (point) nahi hota. range() sirf integers ke saath kaam karta hai; 2.5 jaise number nahi chalte.
5. Function: ek naam wala kaam jo brackets ( ) ke saath bulaya jaata hai, jaise print(). range() bhi Python ka ek built-in function hai, jo numbers ki ek line (sequence) banata hai.
💡 Concept: for Loop aur range() Step-by-Step
🔁 Step 1: for loop ka dhaancha (syntax)
for variable in sequence: # sequence ki har value ke liye ek chakkar body # 4 space andar: har chakkar mein chalegi
variable = woh dibba jismein har chakkar mein agli value aati hai (jaise i, n, seedhi). Ise loop variable kehte hain.
in = “ke andar se” (keyword).
sequence = values ki line, jinpar ek-ek karke chalna hai. Aaj ka sequence hai range().
: = “ab body shuru”.
Ise aise padho: “for seedhi in range(1, 21):” = “1 se 20 tak har seedhi ke liye, neeche ka kaam karo.” Python khud ginti sambhaalta hai; humein update (i = i + 1) likhna hi nahi padta. Isliye for loop mein infinite loop ka khatra bahut kam hota hai.
🔢 Step 2: range() ka pehla roop: range(stop)
Shuruaat apne-aap 0, chhalaang apne-aap 1, aur stop (5) shaamil nahi.
Kyun 0 se? Computer ki duniya mein ginti aksar 0 se hoti hai (jaise list ka pehla item index 0 par). Aur kyun stop shaamil nahi? Taaki range(5) mein theek 5 values aayen. range(n) = “n baar”. Yaad rakhna aasaan!
🔢 Step 3: Doosra roop: range(start, stop)
range(10, 15) → 10, 11, 12, 13, 14
Start shaamil, stop shaamil nahi. Chhalaang ab bhi 1.
Golu ke sawaal ka jawab yahin hai: 1 se 20 tak chahiye toh range(1, 21) likhte hain, kyunki stop par loop pahunchne se pehle ruk jaata hai. Niyam: “aakhri number + 1” stop mein likho. Values kitni? stop − start = 21 − 1 = 20.
🔢 Step 4: Teesra roop: range(start, stop, step)
range(1, 20, 2) → 1, 3, 5, … 19 (odd numbers)
range(5, 51, 5) → 5, 10, 15, … 50 (5 ka pahada)
Step = har baar kitna aage badhna hai.
Kaise chalta hai? Python start se shuru karta hai, har baar step jodta hai, aur jaise hi agla number stop tak pahunche ya usse aage nikal jaaye, ruk jaata hai. range(2, 21, 2) mein 20 ke baad 22 aata, jo 21 se aage hai, isliye ruk gaya.
⬇️ Step 5: Ulti ginti: negative step
range(20, 0, -5) → 20, 15, 10, 5
Ulti ginti mein start bada, stop chhota, aur step minus mein.
Rohan ke sawaal ka jawab: neeche utarna = har baar 1 ghataana = step −1. Yahan bhi stop shaamil nahi: range(10, 0, -1) 1 par khatam hota hai, 0 nahi aata. 0 tak chahiye toh range(10, -1, -1) likho.
🚫 Step 6: Khaali range (loop ek baar bhi nahi)
range(1, 5, -1) → kuch nahi (ulta chalna hai, par 1 se neeche 5 kahan?)
range(0) → kuch nahi
Aisi range par for loop ki body 0 baar chalti hai, koi error nahi aata. Program seedha loop ke neeche wali line par chala jaata hai. Isliye ulti ginti mein minus step bhoolna aam galti hai: range(10, 0) khaali hai!
🖼️ Diagrams: Picture se Samjho
🔐 Deep Concept: range() ke Andar ka Hisaab
1. Values ginne ka formula: range(start, stop, step) mein kitni values hongi? Positive step ke liye: (stop − start) ÷ step, aur agar jawab dashamlav mein aaye toh upar wala poora number lo.
range(1, 100, 3): (100 − 1) ÷ 3 = 33 → 33 values ✔ (1, 4, 7 … 97)
range(0, 50, 7): 50 ÷ 7 = 7.14 → 8 values ✔ (0, 7, 14 … 49)
Python mein yahi ginti len(range(…)) se seedhe mil jaati hai. Exam mein “loop kitni baar chalega?” wale sawaal isi formula se jaldi hal hote hain.
2. range ek “list” nahi, ek “niyam” hai: range(1, 1000000) likhne par Python das lakh numbers memory mein nahi bharta. Woh sirf start, stop aur step yaad rakhta hai, aur loop jab maange tab agla number bana kar deta hai. Isliye bahut badi range bhi memory nahi khaati. Values ek saath dekhni hon toh list(range(…)) likho.
3. Trace table (dry run): neeche ka code kaagaz par chalao:
for i in range(1, 8, 3):
print(i * 10)
| Chakkar | i ki value | i * 10 (output) | Agla number |
|---|---|---|---|
| 1 | 1 | 10 | 1 + 3 = 4 (8 se kam ✔) |
| 2 | 4 | 40 | 4 + 3 = 7 (8 se kam ✔) |
| 3 | 7 | 70 | 7 + 3 = 10 (8 se aage ✘ → ruko) |
Body 3 baar chali. Formula se bhi: (8 − 1) ÷ 3 = 2.33 → upar ka poora number 3. Dono tareeke ek hi jawab dete hain. 🎯
4. Loop ke baad loop variable: loop khatam hone par bhi variable mein aakhri value bachi rehti hai. for i in range(3) ke baad i = 2 hoga (3 nahi!), kyunki 3 kabhi i mein aaya hi nahi.
🧪 Examples: Code, Output aur WHY
Example 1: range(stop): 0 se ginti
for i in range(5): # i ki values: 0, 1, 2, 3, 4 (5 shaamil nahi) print(i) # har chakkar mein i ki us samay ki value chhapo
WHY: start nahi diya toh 0, step nahi diya toh 1. Stop 5 shaamil nahi, isliye aakhri value 4. Kul 5 values = 5 chakkar.
Example 2: range(start, stop) aur ek line mein output
for i in range(1, 11): # 1 se shuru, 11 se pehle ruko: 1 se 10 print(i, end=" ") # end=" " : nayi line ki jagah ek space
WHY: print() aam taur par har baar nayi line par jaata hai. end=” “ kehta hai: “line ke aakhir mein Enter ki jagah ek space daalo”. Isliye saare numbers ek hi line mein aaye.
Example 3: Golu ki seedhiyan (step 2)
for seedhi in range(2, 21, 2): # 2 se shuru, har baar +2, 21 se pehle ruko print(seedhi, end=" ") # Golu ne jis seedhi par pair rakha, woh chhapo
WHY: 2, phir 2+2 = 4, phir 6 … 20. Agla 22 hota, jo stop 21 se aage hai, isliye ruk gaya. Stop 20 likhte toh 20 nahi aata (aakhri value 18 hoti)! Loop variable ka naam seedhi bhi rakh sakte hain: naam aisa rakho jo kaam samjhaaye.
Example 4: Rocket countdown (negative step)
for n in range(10, 0, -1): # 10 se shuru, har baar -1, 0 se pehle ruko print(n, end=" ") # 10 9 8 ... 1 ek line mein print() # loop ke baad: khaali print se nayi line print("Rocket launch! 🚀") # loop ke bahar: sirf ek baar
WHY: step −1 se har baar ghatta hai. Stop 0 shaamil nahi, isliye aakhri value 1. Khaali print() sirf ek nayi line deta hai, taaki “Rocket launch” agli line par aaye.
Example 5: range ki values dekhna aur ginna
print(list(range(1, 10, 3))) # range ki saari values ek list mein dikhao print(list(range(5))) # 0 se 4 print(len(range(2, 21, 2))) # len() batata hai kitni values hain
WHY: print(range(1, 10, 3)) likhoge toh sirf range(1, 10, 3) chhapega, values nahi (kyunki range ek niyam hai). list() use poori line mein badal deta hai. len() values ginta hai: 10 = Golu ke 10 kadam.
Example 6: Khaali range
for i in range(5, 1): # step +1, par 5 se badhte hue 1 tak kabhi nahi pahunchenge print(i) # yeh line ek baar bhi nahi chalegi print("Loop khatam") # loop ke bahar: chalegi
WHY: range(5, 1) mein koi value nahi. Body 0 baar chali, koi error nahi. Ulta ginna tha toh range(5, 1, -1) likhna tha: 5, 4, 3, 2.
Example 7: Loop ke baad variable
for i in range(3): # i: 0, 1, 2 print("Andar:", i) # har chakkar mein print("Bahar:", i) # loop ke baad: i mein aakhri value bachi hai
WHY: aakhri chakkar mein i = 2 tha. Loop rukne par i badalta nahi, isliye bahar bhi 2. (3 kabhi i mein aaya hi nahi, kyunki stop shaamil nahi.)
⚖️ Difference Table: range() ke Teen Roop
| Baat | range(stop) | range(start, stop) | range(start, stop, step) |
|---|---|---|---|
| Kitne numbers dene hain | 1 | 2 | 3 |
| Shuruaat | Hamesha 0 | Aap batate ho | Aap batate ho |
| Chhalaang (step) | Hamesha 1 | Hamesha 1 | Aap batate ho (minus bhi) |
| Ulti ginti? | Nahi | Nahi | Haan (step minus) |
| Udaharan | range(4) → 0, 1, 2, 3 | range(4, 8) → 4, 5, 6, 7 | range(8, 0, -2) → 8, 6, 4, 2 |
| Kab use karein | “n baar” kuch karna ho | Kisi number se kisi number tak | Jump wali ya ulti ginti |
for (range ke saath) vs while
| Baat | for + range() | while |
|---|---|---|
| Kab | Ginti pehle se pata ho | Sirf condition pata ho |
| Update kaun karta hai | Python khud | Hum (n = n + 1 likhna padta hai) |
| Infinite loop ka khatra | Bahut kam | Update bhoole toh zyada |
| Udaharan | for i in range(1, 6): | while i <= 5: |
🚫 Misconceptions (Galat Fehmiyan)
✅ Nahi, stop kabhi shaamil nahi: 1 se 9. 10 tak chahiye toh range(1, 11).
✅ Nahi, yeh khaali range hai (step apne-aap +1). Ulti ginti ke liye range(10, 1, -1) likho.
✅ Ek number wala range hamesha 0 se shuru hota hai: 0, 1, 2, 3, 4.
✅ Nahi, for loop agli value khud deta hai. Likhoge toh bhi agle chakkar mein range ki agli value i mein aa jaayegi.
✅ range() sirf poore numbers (integers) leta hai. Dashamlav dene par TypeError aata hai, aur step 0 dene par ValueError.
✅ Sirf range(0, 5) dikhega. Values dekhni hain toh print(list(range(5))) ya for loop.
🔑 Key Terms
❓ FAQs
1. Stop number shaamil kyun nahi hota? Yeh toh ulta lagta hai!
Iske teen fayde hain: (i) range(n) mein theek n values aati hain, toh “n baar” likhna aasaan. (ii) Values ki ginti seedhe stop − start se mil jaati hai. (iii) Do range jodne par overlap nahi hota: range(0, 5) aur range(5, 10) milkar poora 0 se 9 bante hain, 5 do baar nahi aata. Shuru mein ajeeb lagta hai, par aadat ho jaati hai.
2. Kya step 0 de sakte hain?
Nahi. Step 0 ka matlab “aage hi mat badho”, toh loop kabhi khatam nahi hoga. Python pehle hi rok deta hai: ValueError: range() arg 3 must not be zero.
3. Loop variable ka naam hamesha i hi hona chahiye?
Nahi. Koi bhi sahi variable naam chalega: n, seedhi, roll, number. i ek purani aadat hai (index/integer ka chhota roop). Achha naam code ko padhne mein aasaan banata hai.
4. Ulti ginti mein 0 bhi chahiye toh?
Stop ko 0 se ek aur neeche rakho: range(10, -1, -1) → 10, 9 … 1, 0. Kyunki stop shaamil nahi, isliye −1 tak ka stop dene par 0 aakhri value banti hai.
5. Negative numbers ki range ban sakti hai?
Haan. range(-3, 3) → −3, −2, −1, 0, 1, 2. Aur range(0, -6, -2) → 0, −2, −4. Bas sab integers hone chahiye.
6. end=” ” ke bina kya hoga?
Har print alag line par aayega. end=” ” sirf dikhne ka tareeka badalta hai; loop kitni baar chalega, isse koi fark nahi padta. end=”,” doge toh numbers comma se judenge.
7. Kya for loop sirf range ke saath chalta hai?
Nahi. for kisi bhi sequence par chal sakta hai: string ke har akshar par, list ke har item par. Yeh agle post “for Loop ke Kamaal” mein seekhenge. Aaj ka focus range hai, kyunki ginti wale loops sabse zyada isi se bante hain.
🛠️ Hands-on: AI Tutor mein range() ke saath Khelo
Activity 1: Class mein 5-5 roll number ki baari
for roll in range(1, 31, 5): # roll: 1, 6, 11, 16, 21, 26 (31 shaamil nahi) print("Roll number", roll, "aao!") # har chakkar mein ek bachche ko bulao
WHY yeh kaam karta hai: 1 se shuru, har baar +5. 26 ke baad 31 aata, par stop 31 shaamil nahi, isliye 6 bachche bulaaye gaye. Formula se: (31 − 1) ÷ 5 = 6 ✔. Ab step 10 karke dekho: kitne bachche aayenge? (Jawab: 3 → 1, 11, 21)
Activity 2: Jaan-boojh kar galti, aur use theek karna
Galti A: step 0
for i in range(1, 10, 0):
print(i)
Theek karo: step koi bhi non-zero integer do, jaise range(1, 10, 1). Step 0 se loop kabhi aage nahi badhta, isliye Python mana kar deta hai.
Galti B: dashamlav number
for i in range(2.5):
print(i)
Theek karo: poora number do, jaise range(3). Python mein 2.5 jaise number ko float kehte hain, aur range() sirf integer maangta hai.
Galti C: ulti ginti mein minus step bhoole
for n in range(5, 0):
print(n)
print("Khatam")
Koi error nahi, par loop ek baar bhi nahi chala! Theek karo: range(5, 0, -1) → 5 4 3 2 1. Yeh “chupi hui galti” (logic error) hai, jo sirf output dekh kar pakdi jaati hai.
🎯 Try It Yourself
- 1 se 20 ke beech ke saare odd numbers ek line mein chhapo.
- 100 se 10 tak, 10-10 kam karte hue ulti ginti chhapo.
- 5, 10, 15 … 50 chhapo (5 ke multiples). Bonus: len() se batao kitne numbers hain.
Hints / Solutions
# 1 for i in range(1, 20, 2): print(i, end=" ") # Output: 1 3 5 7 9 11 13 15 17 19 # 2 for i in range(100, 0, -10): print(i, end=" ") # Output: 100 90 80 70 60 50 40 30 20 10 # 3 for i in range(5, 51, 5): print(i, end=" ") print() print(len(range(5, 51, 5))) # Output: 5 10 15 20 25 30 35 40 45 50 # 10
Teeno mein stop ko “aakhri value se ek kadam aage” rakha: 20 (19 ke baad), 0 (10 ke baad ulta), 51 (50 ke baad).
🛡️ Good Habits (Achhi Aadatein)
🧠 Think Like a Programmer
Problem: Mummy ki dukaan par 7 rupaye ka ek pen hai. 1 se 10 pen tak ki keemat ki list chahiye: 7, 14, 21 … 70.
for m in range(7, 71, 7): # 7, 14, 21 ... 70 print(m, end=" ") # ek line mein
🌍 Real Life mein range() wali Soch
- 🏏 Cricket scoreboard: over ki 6 balls = range(1, 7). App har ball ke baad agla number dikhata hai.
- 📅 Calendar app: mahine ke din = range(1, 32) (31 din wale mahine ke liye). Har din ke liye ek dabba banta hai.
- ⏰ Microwave / timer: 10 se 1 tak ulti ginti = range(10, 0, -1).
- 🧾 Dukaan ka bill: 1 se n tak har item ki line chhapna.
- 🏫 School attendance: roll number 1 se 40 tak = range(1, 41); sirf even roll numbers = range(2, 41, 2).
📝 Recap
- for variable in sequence: → sequence ki har value ke liye ek chakkar; update Python khud karta hai.
- range(stop) → 0 se stop − 1 tak. range(start, stop) → start se stop − 1. range(start, stop, step) → har baar step ki chhalaang.
- Stop kabhi shaamil nahi. 1 se n chahiye toh range(1, n + 1).
- Ulti ginti: start bada, stop chhota, step minus: range(10, 0, -1).
- Khaali range par loop 0 baar chalta hai, error nahi aata.
- Values ginne ka formula: (stop − start) ÷ step, upar ka poora number; ya len(range(…)).
- list(range(…)) se values dekho; end=” “ se output ek line mein.
- Step 0 → ValueError; dashamlav number → TypeError.
✍️ Fill in the Blanks
- range(6) ki pehli value ______ hoti hai.
- range() mein ______ value kabhi shaamil nahi hoti.
- Ulti ginti ke liye step ______ hona chahiye.
- range(3, 15, 4) ki values ______ hain.
- range ki values ginne ke liye ______ function use karte hain.
- print(i, end=” “) mein end=” ” nayi line ki jagah ______ lagata hai.
Answers
1) 0 · 2) Stop · 3) Negative (minus) · 4) 3, 7, 11 · 5) len() · 6) Ek space
✅ True / False
- range(1, 5) mein 4 values hain.
- range(10, 1) se 10 se 2 tak ulti ginti hoti hai.
- for loop mein update hamein khud likhna padta hai.
- range(0, 10, 3) ki aakhri value 9 hai.
- range(1, 10, 0) chalane par ValueError aata hai.
- Khaali range par for loop chalane se error aata hai.
Answers (kyun ke saath)
1) True: 1, 2, 3, 4 (5 − 1 = 4).
2) False: step apne-aap +1 hai, toh range khaali hai; range(10, 1, -1) chahiye.
3) False: for loop agli value khud deta hai.
4) True: 0, 3, 6, 9; agla 12 stop se aage.
5) True: step zero allowed nahi.
6) False: body 0 baar chalti hai, koi error nahi.
🔘 MCQs
Q1. range(4) ki values kya hain? (a) 1, 2, 3, 4 (b) 0, 1, 2, 3 (c) 0, 1, 2, 3, 4 (d) 4
✅ (b): ek number wali range 0 se shuru, stop shaamil nahi.
(a) 1 se shuru nahi hoti, aur 4 shaamil nahi.
(c) 4 stop hai, shaamil nahi.
(d) range ek value nahi, values ki line deti hai.
Q2. 1 se 10 tak (10 shaamil) ginti ke liye sahi range? (a) range(10) (b) range(1, 10) (c) range(1, 11) (d) range(0, 10)
✅ (c): stop = aakhri value + 1 = 11.
(a) 0 se 9 deta hai.
(b) 1 se 9 deta hai, 10 chhoot jaata hai.
(d) 0 se 9 deta hai.
Q3. range(2, 10, 2) ki values? (a) 2, 4, 6, 8 (b) 2, 4, 6, 8, 10 (c) 0, 2, 4, 6, 8 (d) 2, 3, 4 … 9
✅ (a): 2 se +2, 10 se pehle ruko.
(b) 10 stop hai, shaamil nahi.
(c) Start 2 diya hai, 0 nahi.
(d) Yeh step 1 ke liye hota.
Q4. range(5, 0, -1) ki values? (a) 5, 4, 3, 2, 1, 0 (b) 0, 1, 2, 3, 4 (c) 5, 4, 3, 2, 1 (d) Khaali
✅ (c): 5 se har baar −1, 0 se pehle ruko.
(a) 0 stop hai, shaamil nahi.
(b) Yeh range(5) hoti.
(d) Minus step diya hai, isliye khaali nahi.
Q5. len(range(10)) ka jawab? (a) 9 (b) 10 (c) 11 (d) 0
✅ (b) 10: 0 se 9 = 10 values.
(a) 9 aakhri value hai, ginti nahi.
(c) 10 shaamil nahi, toh 11 values nahi.
(d) 0 sirf khaali range ka hota.
Q6. for i in range(1, 8, 2): loop kitni baar chalega? (a) 3 (b) 4 (c) 7 (d) 8
✅ (b) 4: 1, 3, 5, 7. (8 − 1) ÷ 2 = 3.5 → 4.
(a) 7 bhi shaamil hai (8 se kam), toh 3 nahi.
(c) 7 values step 1 par hoti.
(d) 8 stop hai.
Q7. range(1.5, 5) chalane par kya hoga? (a) 1.5, 2.5, 3.5, 4.5 (b) 1, 2, 3, 4 (c) TypeError (d) ValueError
✅ (c) TypeError: range sirf integer leta hai; 1.5 float hai.
(a) range dashamlav values nahi banata.
(b) Python khud 1.5 ko 1 nahi banata.
(d) ValueError step 0 par aata hai.
Q8. range(-3, 3) mein kitni values hain? (a) 3 (b) 5 (c) 6 (d) 7
✅ (c) 6: −3, −2, −1, 0, 1, 2. 3 − (−3) = 6.
(a) Sirf positive gine toh 3 lagta, par negative bhi shaamil.
(b) 0 bhi gina jaata hai.
(d) 3 stop hai, shaamil nahi.
🧩 Assertion–Reason
(A) A aur R dono sahi, R, A ko samjhata hai · (B) A aur R dono sahi, par R, A ko nahi samjhata · (C) A sahi, R galat · (D) A galat, R sahi
1. A: range(1, 6) mein 6 shaamil nahi hota. R: range() mein stop value tak pahunchne se pehle hi values ruk jaati hain.
✅ (A): dono sahi, aur R hi A ka kaaran hai.
2. A: range(10, 1) se 10 se ulti ginti hoti hai. R: range() mein step apne-aap 1 hota hai agar na diya jaaye.
✅ (D): A galat hai (range khaali hai), R sahi hai. R hi batata hai ki A kyun galat hai: step +1 se 10 se 1 tak pahuncha hi nahi ja sakta.
3. A: for loop mein infinite loop ka khatra while loop se kam hota hai. R: for loop mein range ki values khatam hote hi loop apne-aap ruk jaata hai.
✅ (A): dono sahi; range seemit (finite) hai aur update Python khud karta hai, isliye loop zaroor rukta hai.
⚡ Very Short Answer
1. range() ke kitne roop hain? Unke naam likho.
Teen: range(stop), range(start, stop), range(start, stop, step).
2. range(3, 7) ki values likho.
3, 4, 5, 6.
3. Ek number wali range ka default start kya hai?
0.
4. range ki saari values ek saath dekhne ke liye kya likhte hain?
print(list(range(…))).
5. Step 0 dene par kaunsi error aati hai?
ValueError.
📄 Short Answer
1. for loop ke syntax ke har hisse ka matlab likho.
for: keyword, “har ek ke liye”. variable: har chakkar mein agli value pakadta hai. in: keyword, “ke andar se”. sequence: values ki line (jaise range). : body shuru. Body 4 space andar.
2. range(1, 20, 3) ki values aur unki ginti batao, formula ke saath.
1, 4, 7, 10, 13, 16, 19. Formula: (20 − 1) ÷ 3 = 6.33 → upar ka poora number 7. Dono se 7 values ✔.
3. Khaali range kya hoti hai? Do udaharan do.
Jis range mein koi value na ho; uspar for loop 0 baar chalta hai aur koi error nahi aata. Udaharan: range(5, 1) (step +1 par aage badh kar 1 tak nahi pahunch sakte) aur range(1, 5, -1).
4. 20 se 0 tak (0 shaamil) 4-4 kam karte hue ginti ka code likho.
for i in range(20, -1, -4): print(i). Values: 20, 16, 12, 8, 4, 0. Stop −1 rakha taaki 0 shaamil ho.
📚 Long Answer
1. range() function ke teeno roop udaharan, values aur use ke saath samjhao. Stop shaamil kyun nahi hota?
(i) range(stop): start 0, step 1. range(4) → 0, 1, 2, 3. “n baar” kaam ke liye.
(ii) range(start, stop): step 1. range(4, 8) → 4, 5, 6, 7. Kisi number se kisi number tak.
(iii) range(start, stop, step): range(8, 0, -2) → 8, 6, 4, 2. Chhalaang wali ya ulti ginti.
Stop shaamil kyun nahi: range(n) mein theek n values aayen; ginti stop − start se seedhe mile; aur range(0, 5) + range(5, 10) bina overlap ke jud jaayein. Isliye 1 se n chahiye toh range(1, n + 1).
2. for loop kaise chalta hai? Flowchart ke shabdon mein aur ek trace table ke saath samjhao (code: for i in range(10, 0, -4): print(i)).
Chalne ka kram: (1) Python range banata hai. (2) Poochhta hai: koi value bachi hai? (3) Haan → agli value i mein rakhta hai, (4) body chalata hai, aur wapas (2) par jaata hai. Nahi → loop khatam, neeche ki line.
Trace: Chakkar 1: i = 10, output 10, agla 6. Chakkar 2: i = 6, output 6, agla 2. Chakkar 3: i = 2, output 2, agla −2 (0 se neeche nikal gaya ✘) → ruko.
Output: 10, 6, 2 (alag-alag lines mein). Loop 3 baar chala. Update (−4) Python ne khud kiya.
🔍 Output Batao / Galti Dhoondho
1. Output batao:for i in range(3, 10, 3):
print(i * 2)
i: 3, 6, 9 (agla 12 stop 10 se aage). Har baar double chhapa.
2. Output batao:for i in range(20, 5, -5):
print(i, end=",")
20, 15, 10; agla 5 stop hai, shaamil nahi. end=”,” se har value ke baad comma (aakhri ke baad bhi).
3. Output batao:c = 0
for i in range(4, 20, 4):
c = c + 1
print(c)
i: 4, 8, 12, 16 → 4 chakkar, har chakkar mein c ek badha. Yeh len(range(4, 20, 4)) ke barabar hai.
4. Galti dhoondho: Rohan 5 se 1 tak ulti ginti chahta hai par kuch nahi chhapta:for x in range(5, 0):
print(x)
Step nahi diya, toh step +1 maana gaya aur range khaali ho gayi. Sahi: range(5, 0, -1) → 5 4 3 2 1.
5. Galti dhoondho: Priya 1 se 10 tak ginti chahti hai:for i in range(1, 10)
print(i)
Do galtiyan: (i) colon nahi hai → SyntaxError. (ii) print indent nahi hai → IndentationError. Aur (iii) logic: 10 tak ke liye stop 11 chahiye. Sahi: for i in range(1, 11): aur agli line mein 4 space ke saath print(i).
🚀 HOTS (Higher Order Thinking)
1. Bina code chalaye batao: range(1, 100, 3) mein kitni values hain aur aakhri value kya hai?
Ginti: (100 − 1) ÷ 3 = 33 (poora aaya) → 33 values. Aakhri value = start + (ginti − 1) × step = 1 + 32 × 3 = 97. Python se check: len() = 33, aakhri = 97 ✔.
2. Golu kehta hai: “Do loop chalaunga: range(0, 5) aur range(5, 10). Kya 5 do baar chhapega?” Samjhao.
Nahi. Pehli range 0 se 4 (5 shaamil nahi), doosri 5 se 9. Milkar 0 se 9, har number ek hi baar. Yahi “stop shaamil nahi” niyam ka bada fayda hai: range ke tukde bina overlap ke jud jaate hain.
3. Ek hi output “10 8 6 4 2” do alag range se kaise banaoge? Dono likho.
(i) Seedhe ulti ginti se: for i in range(10, 0, -2): print(i, end=” “) (range(10, 1, -2) bhi chalega).
(ii) Chhoti range ko double karke: for i in range(5, 0, -1): print(i * 2, end=” “) → 5, 4, 3, 2, 1 ke double = 10 8 6 4 2. Seekh: ek hi problem ke kai sahi hal ho sakte hain.
🏆 Cyber Olympiad Style
1. print(list(range(10, 1, -3))) ka output? (a) [10, 7, 4, 1] (b) [10, 7, 4] (c) [1, 4, 7, 10] (d) []
✅ (b): 10, 7, 4; agla 1 stop hai, shaamil nahi.
(a) 1 stop hai.
(c) Ulti ginti hai, seedhi nahi.
(d) Minus step hai, toh khaali nahi.
2. len(range(0, 50, 7)) = ? (a) 7 (b) 8 (c) 49 (d) 50
✅ (b) 8: 0, 7, 14, 21, 28, 35, 42, 49.
(a) 0 ko ginna bhool gaye toh 7 lagta.
(c) 49 aakhri value hai, ginti nahi.
(d) 50 stop hai.
3. Kaunsi range khaali NAHI hai? (a) range(0) (b) range(3, 3) (c) range(1, 5, -1) (d) range(-5, -1)
✅ (d): −5, −4, −3, −2 (step +1, −5 se −1 ki taraf badhna sambhav).
(a) 0 baar = khaali.
(b) Start = stop, koi value nahi.
(c) Minus step se 1 se 5 tak nahi pahunch sakte.
📚 Aur Padho (External Reference)
- The range() Function: python.org Tutorial (English)
- for Statements: python.org Tutorial (English)
- Ranges: Python Standard Library (range ke niyam detail mein)
- print() aur end · len(): Built-in Functions, python.org
💖 CharuMam Motivation
Chhutti ke baad Golu seedhiyan utar raha tha, aur is baar woh ek-ek seedhi aaram se utra. Priya ne poochha: “Ab chhalaang kyun nahi?” Golu bola: “Upar jaldi pahunchna tha, par neeche girna nahi hai! Step sahi chuno, toh range sahi chalti hai.” 😄
Beta, padhai bhi ek range hai. Start aaj se karo, chahe chhota sa ho. Step apni taakat ke hisaab se chuno: kabhi ek page, kabhi do. Bas step zero mat hone dena, kyunki ruk gaye toh manzil kabhi nahi aayegi. Aur manzil (stop) ko hamesha thoda aage rakhna, taaki aapka sapna poora ho kar hi loop ruke! 🔢🌱
— CharuMam
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