Mastering Negative Indexing in Python

Photo by Farzad on Unsplash

In Python, we have two indexing systems for lists:

• Positive indexing: the first element has the index number 0, the second element has the index number 1, and so on.
• Negative indexing: the last element has the index number -1, the second to last element has the index number -2, and so on.

In practice, we almost always use positive indexing to retrieve list elements. Negative indexing is useful when we want to select the last element of a list — especially if the list is long, and we can’t find the length by counting.

row_1 = ['Facebook', 0.0, 'USD', 2974676, 3.5]

print(row_1[-1])
print(row_1[4])

Output
3.5
3.5

Notice that if we use an index number that is outside the range of the two indexing systems, we’ll get an IndexError.

row_1 = ['Facebook', 0.0, 'USD', 2974676, 3.5]
print(row_1[6])

Output
IndexError: list index out of range