Python me While Loop kya hota hai?

Jab hume ek kaam baar baar karna ho — jab tak koi condition True rahe — tab hum while loop use karte hain. Jaise ek cricket match me batting tab tak chalti hai jab tak batsman out na ho jaye — exactly waise hi while loop kaam karta hai.

Is page me yeh sab sikhenge :-

1. Basic while loop
2. while loop me counter
3. break — loop beech me rokna
4. continue — ek iteration skip karna
5. while-else
6. Infinite loop — aur use kaise sambhalen

Note :- While loop me condition ka False hona zaroori hai warna loop kabhi band nahi hoga — ise Infinite Loop kehte hain. Isliye loop ke andar counter ya update zaroor likhein.

1. Basic while Loop

while loop tab tak chalta rehta hai jab tak condition True ho. Jaise hi condition False hoti hai, loop band ho jata hai.

Syntax
while condition: # yeh code tab tak chalega jab tak condition True ho # counter update karna mat bhoolna!

Example 1: 1 se 5 tak print karna

Python

In [1]:

i = 1

while i <= 5:
    print(i)
    i += 1     # i = i + 1 — yeh na likho toh loop kabhi band nahi hoga!

print("Loop khatam!")

Output

Example 2: Ulti ginti — 10 se 1 tak countdown

Python

In [1]:

n = 10

while n >= 1:
    print(n)
    n -= 1     # har baar 1 kam karo

print("Rocket launch! 🚀")

Output

2. While Loop se Calculations

While loop ka use sirf print karne ke liye nahi, calculations ke liye bhi hota hai — jaise numbers ka sum nikalna, factorial calculate karna, etc.

Example 1: 1 se N tak ka sum nikalna

Python

In [1]:

n = 10
i = 1
total = 0

while i <= n:
    total += i    # total = total + i
    i += 1

print("1 se", n, "tak ka sum:", total)

Output

Example 2: Kisi number ki multiplication table print karna

Python

In [1]:

num = 5
i = 1

print(num, "ka Pahada:")
while i <= 10:
    print(num, "x", i, "=", num * i)
    i += 1

Output

Example 3: Factorial calculate karna (n!)

Python

In [1]:

n = 6
i = 1
factorial = 1

while i <= n:
    factorial *= i    # factorial = factorial * i
    i += 1

print(n, "! =", factorial)    # 6! = 720

Output

3. break Statement

break ka use karke hum loop ko beech me hi band kar sakte hain — chahe condition abhi bhi True ho. Jaise exam me ek baar answer mil gaya toh aage dekhna band karo.

Example 1: 5 aate hi loop band karo

Python

In [1]:

i = 1

while i <= 10:
    if i == 5:
        print("5 mil gaya! Loop band karte hain.")
        break        # loop yahan rok do
    print(i)
    i += 1

print("Loop ke baad")

Output

Example 2: ATM PIN — 3 galat tries ke baad block karo

Python

In [1]:

correct_pin = 1234
tries = 0
attempts = [1234, 9999, 5678]   # user ke attempts simulate kar rahe hain

while tries < 3:
    entered = attempts[tries]
    tries += 1
    print(f"Attempt {tries}: PIN {entered} enter kiya")

    if entered == correct_pin:
        print("Sahi PIN! Access granted.")
        break
    else:
        print("Galat PIN!")

if tries == 3 and attempts[tries-1] != correct_pin:
    print("3 baar galat — Card block ho gaya!")

Output

4. continue Statement

continue ek iteration ko skip kar deta hai aur loop agli iteration se aage chalta rehta hai. break ki tarah loop band nahi hota — sirf uss ek step ko chhod deta hai.

Example 1: 1 se 10 me sirf odd numbers print karo

Python

In [1]:

i = 0

while i < 10:
    i += 1
    if i % 2 == 0:
        continue     # even number aaye toh skip karo
    print(i)         # sirf odd numbers print honge

Output

Example 2: 1 se 20 me 3 ke multiples skip karo

Python

In [1]:

i = 0

print("3 ke multiples chhodkar baaki numbers:")
while i < 20:
    i += 1
    if i % 3 == 0:
        continue    # 3 ka multiple? skip!
    print(i, end=" ")

Output

5. while-else Statement

Python me while ke saath else bhi likh sakte hain. else wala block tab chalta hai jab loop normally khatam ho — yaani condition False ho gayi ho. Agar loop break se band hua ho toh else nahi chalega.

Example 1: Normal loop — else chalega

Python

In [1]:

i = 1

while i <= 5:
    print(i)
    i += 1
else:
    print("Loop normally khatam hua — else chala!")

Output

Example 2: break se band — else nahi chalega

Python

In [1]:

i = 1

while i <= 5:
    if i == 3:
        print("3 par break kiya!")
        break
    print(i)
    i += 1
else:
    # break se loop band hua isliye yeh nahi chalega
    print("Yeh print NAHI hoga")

Output

6. Infinite Loop

Jab while loop ki condition kabhi False nahi hoti toh loop hamesha chalta rehta hai — isse Infinite Loop kehte hain. Yeh zyaadatar galti se hota hai, lekin kabhi kabhi jaanboojhkar bhi use kiya jaata hai (jaise server programs). Isse rokne ke liye break use karte hain.

Example 1: while True — break se control karna

Python

In [1]:

count = 0

while True:    # yeh hamesha True rahega
    count += 1
    print("Iteration:", count)

    if count == 5:
        print("5 tak pahuncha — ab band karte hain!")
        break  # break nahi hota toh yeh kabhi band nahi hota

Output

Example 2: Common galti — counter update bhool jana (simulated)

Python

In [1]:

# GALAT tarika — i += 1 nahi likha toh infinite loop ban jata
# i = 1
# while i <= 5:
#     print(i)
#     # i += 1 — yeh bhool gaye! Ab i hamesha 1 rahega

# SAHI tarika — hamesha counter update karo
i = 1
while i <= 5:
    print(i)
    i += 1    # yeh ZAROORI hai!

print("Loop sahi se khatam hua!")

Output

Quick Summary — while loop ek nazar me

Concept	Kaam	Example
while	Condition True hone tak loop chalaao	while i <= 5:
break	Loop beech me rokna	if i == 3: break
continue	Ek step skip karna	if i % 2 == 0: continue
while-else	Loop normally khatam ho toh else chalao	while ...: ... else: ...
while True	Infinite loop — break se rokna padta hai	while True: ... break

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