String Indexing in Python

In this lesson of the Nigiara Python course, I will explain how string indexing works.

What is indexing? In Python, strings (text) are a sequence of characters. For example, a word or phrase can be seen as a combination of individual characters placed one after the other. Each character within a string has an index, which is a numeric position within the string itself.

The first character of a string has an index of 0, the second character has an index of 1, and so on. String indexing is the process of accessing a specific character within a string using its index.

In Python, string indexing works similarly to accessing elements of a list.

Strings in Python are iterable objects. Therefore, you can read each character within a string using its numeric index.

To access a specific character within a string, you need to indicate the index of the character in square brackets.

string[index]

Here's a practical example.

Assign a string to the variable "text".

>>> text = "Python is a programming language"

To read the first character of the string, type text[0]

>>> text[0]

In this case, the command returns the letter "P", because it is the first letter of the string "Python is a programming language".

P

Remember that indexing always starts at 0, not 1. So the first character of a string always has index 0.

Now type text[1] to read the second character of the string.

>>> text[1]

The output result is the character "y".

y

In Python, string indexing can also be a negative number.

In this case, the index starts from the last character of the string, where -1 corresponds to the last character, -2 to the second-to-last, and so on.

For example, type text[-1]

>>> text[-1]

Python accesses the last character of the string and returns the character "e".

Now type the command text[-2]

>>> text[-2]

The result is the second-to-last character of the string, which is "g".

In short, string indexing in Python allows you to access individual characters within a string through their index number, which can be both positive and negative. With a positive index, you access characters from the first to the last, from left to right, while with a negative index, you access characters from the last to the first, from right to left.