Loops, Iterators, and Repetition Control in Python

1. Definite Repetition: The for Loop

Used to iterate over iterable objects like lists, strings, or ranges.

for i in range(5):  
    print("Hello", i)

Output:
Hello 0  
Hello 1  
Hello 2  
Hello 3  
Hello 4

2. Indefinite Repetition: The while Loop

Repeats until a condition becomes False.

x = 0  
while x < 3:  
    print("x =", x)  
    x += 1

3. Getting User Input: input()

The input() function prompts the user and returns a string.

name = input("What's your name? ")  
print("Hello", name)

4. Iterators in Python

Any iterable object like a list or string can be converted into an iterator.

my_list = [10, 20, 30]  
iterator = iter(my_list)  
print(next(iterator))  # 10  
print(next(iterator))  # 20  
print(next(iterator))  # 30

5. enumerate: Counting While Iterating

for index, value in enumerate(["a", "b", "c"]):  
    print(index, value)

6. zip: Parallel Iteration

names = ["Ali", "Sara"]  
scores = [80, 90]  
for name, score in zip(names, scores):  
    print(name, score)

7. shuffle: Randomize a List

From the random module, used to reorder list items randomly.

import random  
items = [1, 2, 3, 4]  
random.shuffle(items)  
print(items)

8. Combining Loops and input()

Example of infinite repetition until a condition is met:

while True:  
    answer = input("Type 'exit' to quit: ")  
    if answer == "exit":  
        break

9. Conclusion

Understanding loops, iterators, and repetition control — along with tools like `input`, `zip`, `enumerate`, and `shuffle` — empowers you to build flexible and intelligent programs. Loops are at the heart of many real-world algorithms, and mastering them makes your Python code truly dynamic.