Lesson 07 — Logic

REPEAT KARO.
SOCH SAMJH KAR.

Ek student ka result print karna easy hai. 500 students ka? Same instruction ko manually copy karna bad idea hai. Loop ek controlled repeat mechanism hai — aur control hi important word hai.

FOR: collection ke har item par kaam

Jab aapke paas list, string ya kisi ordered sequence ke items hain, for natural choice hai. Loop variable har turn mein current item hold karta hai.

skills = ["Python", "SQL", "Pandas"]

for skill in skills:
 print("Learning:", skill)

Read it literally: "skills mein har skill ke liye, Learning + skill print karo." skill variable sirf loop body ke context mein current value ko describe kar raha hai.

range(): fixed number of repeats

range(3) values 0, 1, 2 deta hai. End value included nahi hoti. Count ka intent clear ho to range(1, 4) readable ho sakta hai—1, 2, 3.

for day in range(1, 4):
 print(f"Day {day}: practice complete")

WHILE: jab end condition se decide ho

while tab tak run karega jab tak condition true hai. Ismein update line mandatory socho — warna condition kabhi false nahi hogi aur infinite loop ban sakta hai.

break aur continue kab?

• break loop ko immediately stop karta hai — example: required record mil gaya.
• continue current turn skip karta hai aur next item par jaata hai — example: blank row ignore karni hai.
• In dono ko only clear purpose ke liye use karo; nested logic se escape karne ke liye nahi.

# Unpythonic: flag variable
found = False
for m in [72, 91, 65]:
    if m > 90:
        found = True
        break

# Pythonic: for-else
for m in [72, 91, 65]:
    if m > 90:
        print("topper mila")
        break
else:
    print("koi topper nahi")

for i, name in enumerate(["Aman", "Priya"]):
    print(i, name)  # index free me

MNC tip: enumerate + zip + for-else — teeno ek saath aane chahiye.

Debugging checklist

• Loop body correctly indented hai?
• while condition ko false banane wala update har turn mein ho raha hai?
• Index manually use karna zaruri hai ya direct for item in items better hai?
• range ka last value exclude hota hai — off-by-one errors yahin se aate hain.