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[Tut] Python Reverse List with Slicing — An Illustrated Guide

Python Reverse List with Slicing — An Illustrated Guide

Summary: The slice notation `list[::-1]` with default `start` and `stop` indices and negative step size `-1` reverses a given `list`.

Problem: Given a list of elements. How to reverse the order of the elements in the list.

Example: Say, you’ve got the following list:

`['Alice', 'Bob', 'Carl', 'Dora']`

Your goal is to reverse the elements to obtain the following result:

`['Dora', 'Carl', 'Bob', 'Alice']`

## Slicing with Default Start and Stop Values

Slicing is a concept to carve out a substring from a given string.

Use slicing notation `s[start:stop:step]` to access every `step`-th element starting from index `start` (included) and ending in index `stop` (excluded).

All three arguments are optional, so you can skip them to use the default values (`start=0`, `stop=len(lst)`, `step=1`). For example, the expression `s[2:4]` from string `'hello'` carves out the slice `'ll'` and the expression `s[:3:2]` carves out the slice `'hl'`. Note that slicing works the same for lists and strings.

You can use a negative step size (e.g., -1) to slice from the right to the left in inverse order. Here’s how you can use this to reverse a list in Python:

```# Reverse a List with Slicing
names = ['Alice', 'Bob', 'Carl', 'Dora']
names = names[::-1]
print(names)
# ['Dora', 'Carl', 'Bob', 'Alice']```

Python masters know slicing from the inside out. Do you want to improve your slicing skills? Check out my book “Coffee Break Python Slicing” that will make you a slice pro in no time!

## Alternatives Reversing List

Alternatively, you can also use other methods to reverse a list.

• `list.reverse()` — Best if you want to reverse the elements of list in place.
• `list[::-1]` — Best if you want to write concise code to return a new list with reversed elements.
• `reversed(list)` — Best if you want to iterate over all elements of a list in reversed order without changing the original list.

The method `list.reverse()` can be 37% faster than `reversed(list)` because no new object has to be created.

Try it yourself in our interactive Python shell:

Exercise: Run the code. Do all methods result in the same reversed list?

## Where to Go From Here?

Enough theory, let’s get some practice!

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Practice projects is how you sharpen your saw in coding!

Do you want to become a code master by focusing on practical code projects that actually earn you money and solve problems for people?

Then become a Python freelance developer! It’s the best way of approaching the task of improving your Python skills—even if you are a complete beginner.

Join my free webinar “How to Build Your High-Income Skill Python” and watch how I grew my coding business online and how you can, too—from the comfort of your own home.

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The post Python Reverse List with Slicing — An Illustrated Guide first appeared on Finxter.

https://www.sickgaming.net/blog/2020/10/...ted-guide/

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