# Slice Notation on List in Python

Hello, Coders!! In this Python tutorial, we will learn about the slice notation on a list in a Python program.

Before diving into the main topic, let’s discuss some basic concepts first;

1. List in Python
2. Slice notation in Python

## List in Python

In Python, a List is considered as a data structure that is mutable or changeable in nature. It is an ordered sequence of elements.

The elements or the data values of a list are also called as items. It is defined by the elements placed inside square brackets `[]`. It can include multiple number of items of different data types(int, float, char, etc).

Syntax:

`list_name[item1, item2, item3,....]`

Example:

`bookstore = ['pen', 'book', 'eraser', 'marker', 'notebook']`

Output:

```['pen','book','eraser','marker','notebook']
```

## Slice Notation In Python

The slice nation is used to return a portion of any list, string, tuple, etc. In other words, we can say it is used to obtain a sublist, sub-tuple, substring from a list, tuple, and substring respectively.

Syntax:

`a[start:stop:step]`

It is the common syntax for the slice notation, where the `start` is the index of the first element(included), `stop` is the index before which to stop (not included) and `step` is the stride between any two elements.

We can also use the slice notation by omitting the argument according to our requirement:

```a[start:]  //Start from the given index till the last of the array
a[1:]  ⇾  starts at index 1 and stop the end of the array
a[:stop]   // Start from the first index to stop - 1 index of the array
a[:4]   ⇾  starts at index 0 and stops before index 4

a[start:stop]   // Start from the given index to stop - 1 index of the array
a[1:4]   ⇾  starts at index 1 and stops before index 4

a[:]       // A copy of the whole array
a[:]    ⇾  starts at index 0 and stop at the end of the array

a[start::step] // Start from the given index to last index of the array with a stride
a[2::2] ⇾ starts at index 2 and stops at the end of the array,every 2nd element```

The `start`, `stop` and `step` maybe a negative number. In such a case, it counts the items from the last index of the  array instead of from the start.

Example:

```a[-1]   ⇾ Last item of the array
a[-3:]  ⇾ Last 3 item in the array
a[: -1] ⇾ Every element except the last element
a[::-1] ⇾ All elements in a reversed order```

## Slicing a List in Python

Example1:

We can slice a list using the parameters discussed before. Let’s take a list of strings and then try to slice that list without any stride or step parameter.

```season_india = ['autumn','Summer','Winter','Spring','fall','monsoon']
season_global = season_india[1:5]
print(season_global)```

Output:

`['Summer', 'Winter', 'Spring', 'fall']`

Example2:

Slicing the list with a stride parameter:

```season_india = ['autumn','Summer','Winter','Spring','fall','monsoon']
season_global = season_india[:5:2]
print(season_global)
```

Output:

```['autumn', 'Winter', 'fall']
```

Example3:

Slicing the list from the first index to a given index and from a given index to the last index of the array.

```season_india = ['autumn','Summer','Winter','Spring','fall','monsoon']
season_global1 = season_india[:5]
season_global2 = season_india[1:]
print(season_global1)
print(season_global2)```

Output:

```['autumn', 'Summer', 'Winter', 'Spring', 'fall']
['Summer', 'Winter', 'Spring', 'fall', 'monsoon']```

Example4:

Slicing the list to print the last 3 elements and to print every element except the last 3 elements.

```season_india = ['autumn','Summer','Winter','Spring','fall','monsoon']
season_global1 = season_india[:-3] //excluding the last 3 elements
season_global2 = season_india[-3:] //Printing the last 3 elements
print(season_global1)
print(season_global2)```

Output:

```['autumn', 'Summer', 'Winter']
['Spring', 'fall', 'monsoon']```

Hope this tutorial has helped you understand the concept of slicing notation and how we can slice a list in a Python program.

Happy Coding!!!

You can also read, How to run a Python file in Linux – Step-by-Step Guide