April Python Bootcamp Day 6 - Loops

 

Day 6: Loops in Python 

Loops are one of the most powerful concepts in programming. They allow you to execute code repeatedly, automate tasks, and handle large data efficiently.

In today’s session, we’ll cover:

• For Loop
• While Loop
• Break & Continue
• Loop Else Concept (Important & Unique to Python)

---

 Why Loops Matter?

Imagine:

• Printing numbers from 1 to 100
• Processing thousands of users
• Running a condition until it's satisfied

Without loops → repetitive code ❌
With loops → clean & efficient code ✅

---

 FOR LOOP

 What is a For Loop?

A for loop is used to iterate over a sequence (list, string, tuple, etc.).

 Syntax

for variable in iterable:
    # code block

---

 How It Works

• Takes one element at a time from iterable
• Assigns it to variable
• Executes the block
• Repeats until iterable ends

---

 Example

for i in range(5):
    print(i)

 Output:

0
1
2
3
4

---

 Understanding range()

range(start, stop, step)

Examples:

range(5)        # 0 to 4
range(1, 5)     # 1 to 4
range(1, 10, 2) # 1, 3, 5, 7, 9

---

 Looping Through Data Types

String

for ch in "Python":
    print(ch)

List

for num in [10, 20, 30]:
    print(num)

---

 FOR-ELSE (Important Concept)

for i in range(3):
    print(i)
else:
    print("Loop completed")

else runs only if loop doesn't break

---

 WHILE LOOP

 What is a While Loop?

Executes code as long as condition is True

---

 Syntax

while condition:
    # code block

---

 Example

i = 0
while i < 5:
    print(i)
    i += 1

 Infinite Loop

while True:
    print("Running...")

 Runs forever unless stopped manually

---

 WHILE-ELSE

i = 0
while i < 3:
    print(i)
    i += 1
else:
    print("Done")

 Runs only if loop ends normally (no break)

---

 BREAK STATEMENT

Stops loop immediately

for i in range(5):
    if i == 3:
        break
    print(i)

---

 CONTINUE STATEMENT

Skips current iteration

for i in range(5):
    if i == 2:
        continue
    print(i)

---

 FOR vs WHILE

Feature	For Loop	While Loop
Based on	Iterable	Condition
Use Case	Known iterations	Unknown iterations
Risk	Safe	Can become infinite

---

 Key Takeaways

• for loop → iterate over data
• while loop → run until condition fails
• break → stops loop
• continue → skips iteration
• else → runs only if loop completes normally

---

 Practice Questions

 Basic

• Print numbers from 1 to 10 using for loop
• Print numbers from 10 to 1 using while loop
• Print all characters in a string
• Print even numbers from 1 to 20

---

 Intermediate

• Sum of first n numbers
• Multiplication table of a number
• Count digits in a number
• Reverse a number

---

 Advanced

• Check if number is prime (use loop + break + else)
• Fibonacci series
• Pattern printing (triangle)
• Menu-driven program using while loop