For Loops and Ranges

In programming, we often need to repeat a task multiple times. A for loop is used for definite iteration, which means we know exactly how many times the code should run before it even starts. Think of it like a train track with a specific number of stations; the train (your code) must stop at every station until it reaches the end. In Python, we use the `for` keyword combined with the `range()` function to tell the computer how many 'stations' to visit. The variable we define in the loop, often called $i$ (for index), acts as a counter that keeps track of which iteration we are currently on.

The `range()` function is more powerful than it looks. It can actually take three different 'arguments' or inputs: start, stop, and step. The syntax looks like this: `range(start, stop, step)`. - Start: The first number in your sequence (default is $0$). - Stop: The limit where the loop ends (not included in the output). - Step: How much to add to the number each time (default is $1$). By changing the step, you can count by twos, tens, or even count backwards by using a negative number like $-1$!

Choosing the right tool makes coding easier. Use a for loop when you know the number of repetitions in advance (e.g., 'Do this 10 times' or 'Do this for every item in a list'). Use a while loop when you don't know how long it will take, and you are waiting for a specific condition to change (e.g., 'Keep playing the game until the player hits a wall'). A for loop is like a scheduled bus route, while a while loop is like a taxi driving until the passenger says 'Stop!'