Loops

1. Counting Positive Numbers

Problem: Given a list of numbers, count how many are positive.

```python

numbers = [1, -2, 3, -4, 5, 6, -7, -8, 9, 10]

```

numbers = [1, -2, 3, -4, 5, 6, -7, -8, 9, 10]
positive_number_count = 0

for num in numbers:
    if num > 0:
        positive_number_count += 1

print("Final count of positive number is: ", positive_number_count)

2. Sum of Even Numbers

Problem: Calculate the sum of even numbers up to a given number n.

n = 10
sum_even = 0

for i in range(1, n+1):
    if i%2 == 0:
        sum_even += 1

print("Sum of even number is: ", sum_even)

3. Multiplication Table Printer

Problem: Print the multiplication table for a given number up to 10, but skip the fifth iteration.

number = 3

for i in range(1, 11):
    if i == 5:
        continue
    print(number, 'x', i, '=', number*i)

4. Reverse a String

Problem: Reverse a string using a loop.

input_str = "Python"
reversed_str = ""

for chai in input_str:
    reversed_str = chai + reversed_str

print(reversed_str)

5. Find the First Non-Repeated Character

Problem: Given a string, find the first non-repeated character.

input_str = "teeteracdacd"

for char in input_str:
    print(char)
    if input_str.count(char) == 1:
        print("Char is: ", char)
        break

Factorial Calculator

Problem: Compute the factorial of a number using a while loop.

number = 5

factorial = 1

while number > 0:
    factorial *= number
    number -= 1

print("Factorial: ", factorial)

Validate Input

Problem: Keep asking the user for input until they enter a number between 1 and 10.

while True:
    number = int(input("Enter value b/w 1 and 10"))
    if 1 <= number <= 10:
        print("Thanks!")
        break
    else:
        print("Invalid number, try again")

8. Prime Number Checker

Problem: Check if a number is prime.

number = 28

is_prime = True

if number > 1:
    for i in range(2, number):
        if(number % i) == 0:
            is_prime = False
            break

print(is_prime)

9. List Uniqueness Checker

Problem: Check if all elements in a list are unique. If a duplicate is found, exit the loop and print the duplicate.

```python

items = [“apple”, “banana”, “orange”, “apple”, “mango”]

```

items = ["apple", "banana", "orange", "apple", "mango"]

unique_item = set()

for item in items:
    if item in unique_item:
        print("Duplicate: ", item)
        break
    unique_item.add(item)

10. Exponential Backoff

Problem: Implement an exponential backoff strategy that doubles the wait time between retries, starting from 1 second, but stops after 5 retries.

import time

wait_time = 1
max_retries = 5
attempts = 0

while attempts < max_retries:
    print("Attempt", attempts + 1, "- wait time", wait_time, )
    time.sleep(wait_time)
    wait_time *= 2
    attempts += 1