Which list will be referenced by the variable list_strip after the execution of the following code? Show
list_string = '03/07/2008' a. ['3', '7', '2008'] Sets with similar termsIn Python, you can start indexing from the end of an iterable. This is known as negative indexing. For example, let’s get the last value of a list: numbers = [1, 2, 3, 4, 5] last = numbers[-1] print(last) Output: 5 Here is an illustration of how the list indexing works in Python: This means you can use both positive and negative indexes to access iterables. In this guide, you learn about negative indexing and its applications in Python. To access elements of a Python iterable, such as a list, you need to know the index of the element. Python supports indexing in two ways:
Let’s take a closer look at both of these. Zero-Based Indexing in PythonThe basic way to access iterable elements in Python is by using positive zero-based indexing. This means each element in the iterable can be referred to with an index starting from 0. In zero-based indexing, the 1st element has 0 index, the 2nd element has 1, and so on. Here is an illustration: For example, let’s get the first name in a list of names: names = ["Alice", "Bob", "Charlie", "David", "Emmanuel", "Fiona"] first = names[0] print(first) Output: Python Negative “From the End” Indexing in PythonPython supports “indexing from the end”, that is, negative indexing. This means the last value of a sequence has an index of -1, the second last -2, and so on. You can use negative indexing as your advantage when you want to pick values from the end (right side) of an iterable. For instance, let’s get the last three names from a list of names: names = ["Alice", "Bob", "Charlie", "David", "Emmanuel", "Fiona"] last = names[-1] second_last = names[-2] third_last = names[-3] print(last, second_last, third_last) Output: Fiona Emmanuel David Slicing and Indexing in PythonNegative indexing is really useful with slicing iterables in Python. If you are unfamiliar with the concept of slicing, please read this article. Slicing in a NutshellIn short, slicing means retrieving the desired subsequence of a sequence in Python. Slicing iterable returns a slice object. This is a part of the iterable, such as the first three numbers of a list of ten numbers. Slicing follows this syntax: iterable[start:stop:step] Where:
For example, let’s get the first three names from a list of names: names = ["Alice", "Bob", "Charlie", "David", "Emmanuel", "Fiona"] first_three = names[0:3:1] print(first_three) Output: ['Alice', 'Bob', 'Charlie'] It is useful to know:
So the above example becomes: first_three = names[:3] Slicing “From the End” with Negative IndexesIn Python, slicing supports negative indexing too. This makes it easier to slice iterables from the end. For instance, let’s get the last three names from the list: names = ["Alice", "Bob", "Charlie", "David", "Emmanuel", "Fiona"] last_three = names[-3:] print(last_three) Output: ['David', 'Emmanuel', 'Fiona'] Negative slicing also supports negative step size. This makes the slicing go backward. For example, let’s reverse the list of names. To do this, you do not need start and stop parameters, as you start from the beginning and stop at the end: names = ["Alice", "Bob", "Charlie", "David", "Emmanuel", "Fiona"] last_three = names[::-1] print(last_three) Output: ['Fiona', 'Emmanuel', 'David', 'Charlie', 'Bob', 'Alice'] ConclusionToday you learned how to start indexing from the end of an iterable in Python. To recap, Python supports positive zero-based indexing and negative indexing that starts from -1. Negative indexing in Python means the indexing starts from the end of the iterable. The last element is at index -1, the second last at -2, and so on. Thanks for reading. Happy coding! Further Reading50 Python Interview Questions What is the first negative index in a list Python?What is the first negative index in a list? The index – 1 identifies the last element in a list. What method or operator can be used to concatenate lists?
What does [Python also allows you to index from the end of the list using a negative number, where [-1] returns the last element. This is super-useful since it means you don't have to programmatically find out the length of the iterable in order to work with elements at the end of it.
What is negative indexing in string in Python?Negative Indexing is used to in Python to begin slicing from the end of the string i.e. the last. Slicing in Python gets a sub-string from a string. The slicing range is set as parameters i.e. start, stop and step.
What does a negative index mean?What are negative indices? Negative indices are powers (also called exponents) with a minus sign in front of them. E.g. x−2. 3−4.
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