🚀 Introduction to Loops in Python: Simplify Repetition with Ease! 🔄

Introduction to Loops in Python

Loops allow us to execute a block of code multiple times. Python primarily supports two types of loops:

for loop
while loop

The `for` Loop

The for loop is used to iterate over sequences like strings, lists, tuples, sets, or dictionaries.

Example: Iterating Over a String

city = 'Mumbai'
for char in city:
    print(char, end="-")

Output:

M-u-m-b-a-i-

Example: Iterating Over a List

fruits = ["Apple", "Banana", "Cherry", "Mango"]
for fruit in fruits:
    print(fruit)

Output:

Apple  
Banana  
Cherry  
Mango

The `range()` Function

The range() function helps us loop over a sequence of numbers.

Default Range Example

for num in range(6):
    print(num)

Output:

By default, the loop starts at 0 and increments by 1.

Range With Start and End

for num in range(3, 8):
    print(num)

Output:

The loop starts at 3 and stops before 8.

Quick Quiz: Third Parameter in `range()`

The third parameter in the range() function is the step value (increment or decrement).
Syntax: range(start, stop, step)

Example: Using Step in `range()`

for num in range(1, 10, 3):  # Increment by 3
    print(num)

Output:

1  
4  
7

Example: Using Negative Step

for num in range(10, 2, -2):  # Decrement by 2
    print(num)

Output:

Conclusion

Use for loops to iterate over any sequence like strings, lists, or dictionaries.
Use range() to loop a specific number of times with optional start, stop, and step values.
Practice using the third parameter in range() for custom increments or decrements! 🚀

Practical:

name = "safia"
for cute in name: # for loop
   print(cute)

fruits = ["apple", "kiwi","grapes"]
for fruit in fruits:
  print(fruit)   #itirate list

for num in range(1,1001): # range
  print(num)

for num in range(1,10,2):
   print(num) #increment

for num in range(10,2,-2):
   print(num) #decrement

Check Even or Odd Numbers :

# Loop through numbers 1 to 5
for number in range (1,20):  # Numbers from 1 to 19
   if number % 2 == 0: # Check if the number is divisible by 2
      print(number, "Is Even")  # Print this if the number is even
   else:
      print(number,"Is Odd")  # Print this if the number is odd

While Loops in Python :

Python `while` Loop

The while loop is used to repeat a block of code as long as a condition is True. When the condition becomes False, the loop stops.

Simple Example: Count Down Numbers

number = 3  # Start from 3
while number > 0:  # Run the loop while the number is greater than 0
    print(number)  # Print the current number
    number = number - 1  # Decrease the number by 1

Output:

3
2
1

Explanation:

The loop starts with number = 3.
The condition number > 0 is checked.
Inside the loop:
- It prints the current value of number.
- Then decreases number by 1 (number = number - 1).
The loop stops when number becomes 0.

Else with `while` Loop

You can add an else block to the while loop. The else block will run when the while loop condition becomes False.

Simple Example with `else`

number = 3  # Start from 3
while number > 0:  # Run the loop while the number is greater than 0
    print(number)  # Print the current number
    number = number - 1  # Decrease the number by 1
else:
    print("The loop has ended!")  # This runs when the condition becomes False

Output:

3
2
1
The loop has ended!

Explanation:

The else block runs after the while loop ends.
When number becomes 0, the condition number > 0 is False.
At this point, the program moves to the else block and prints "The loop has ended!".

Why Use the `else` Block?

The else block can be used for:

Printing a final message after the loop ends.
Adding extra logic to handle the loop termination.

Interesting Python Programs Using Loops and Conditions :

Guess the Secret Number Game :

secret_number = 9
attempts = 3

print("Guess Karo Bhai Secret Number between 1 and 10!")

while attempts > 0:
    guess = int(input("Enter your guess: "))
    if guess == secret_number:
        print("🎉 Correct! You guessed it!")
        break
    elif guess > secret_number:
        print("Too high! Try again.")
    else:
        print("Too low! Try again.")
    attempts -= 1

if attempts == 0:
    print("😢 Sorry, you've run out of attempts. The secret number was", secret_number)

Multiplication Table :

num = int(input("Enter a number: "))
print (f"Multipilication Table of {num}")
for mul in range (1,11):
 print(f"{num} x {mul} = {num * mul}")

what is f ?

To use an f-string, write the string with an f prefix and include variables or expressions inside curly braces {}. Python will replace the curly braces with the actual value.

name = "Safia"
age = 24

# Using f-string
print(f"My name is {name} and I am {age} years old.")

Password Checker :

correct_password = "safia123"
attempts = 3

while attempts > 0:
    password = input("Enter the password: ")
    if password == correct_password:
        print("✅ Access Granted!")
        break
    else:
        print("❌ Incorrect password. Try again.")
    attempts -= 1

if attempts == 0:
    print("⛔ Too many attempts. Access Denied.")

Reverse a Word :

word = input("Enter a word to reverse: ")
reversed_word = ""

for char in word:
      reversed_word = char + reversed_word

print("Reversed word:", reversed_word)

🚀 Introduction to Loops in Python: Simplify Repetition with Ease! 🔄