Iterating with range() Function

Imagine you have a list of travel destinations and you want to work with only a specific part of it. For example, you might want to visit just the first three cities or print destinations in reverse order. Python's range() function can help you iterate over the indices of the list easily!

Why use range()?

• The range() function is useful when working with list indices;
• It allows you to control the start, end, and step of iteration;
• Instead of iterating directly over the items, you iterate over the positions of items in a sequence.

Syntax of range()

The format of the range() function is:

• start: the starting index of the range (default is 0 if omitted);
• end: the ending index (exclusive);
• step: the increment between indices (default is 1).

Example 1: Printing Specific Destinations

Suppose we have a list of cities we want to visit. Let's print the first three destinations using range():

Explanation:

1. range(3) generates numbers from 0 to 2 (end value 3 is exclusive);
2. Inside the loop, travel_list[i] accesses the destination at index i.

Example 2: Printing Destinations in Reverse

Let's print the travel destinations in reverse order:

Explanation:

1. len(travel_list) calculates the number of items in the list (5 in this case);
2. range(len(travel_list) - 1, -1, -1) generates indices from 4 to 0;
3. The loop accesses travel_list[i] in reverse order and prints:

Note

Often, we don't know the length of a list in advance. To handle this, we calculate the length of the list using the len() function.

Since Python's list indexing starts at 0, the last element's index is always len(list) - 1. For example, if a list has 5 elements, the last element is at index 4 (not 5).