subscriptable meaning in python with code examples

Subscriptable in Python refers to the ability of an object to be indexed or sliced, meaning that it can be accessed by using square brackets ([]). In Python, the most common subscriptable objects are lists, tuples, and strings. However, any object that implements the "getitem" method can be considered subscriptable. In this article, we'll explore the meaning of subscriptable in Python, how to make objects subscriptable, and provide code examples for better understanding.

First, let's look at the built-in subscriptable objects in Python. Lists, tuples, and strings can all be indexed or sliced. For example, consider the following list:

>>> numbers = [1, 2, 3, 4, 5]
>>> numbers[0]
1
>>> numbers[1:3]
[2, 3]

Here, we've defined a list called "numbers", and we've used square brackets to access the first element of the list (numbers[0]), which returns 1. We've also sliced the list to get a sublist (numbers[1:3]), which returns [2, 3].

Similarly, you can index and slice tuples and strings:

>>> name = "John Doe"
>>> name[0]
'J'
>>> name[1:5]
'ohn '

>>> coordinates = (1, 2, 3)
>>> coordinates[0]
1
>>> coordinates[1:2]
(2,)

In the case of tuples, the slicing returns a new tuple, while in the case of strings, the slicing returns a new string.

Now, let's see how we can make our own objects subscriptable. To do this, we need to define the "getitem" method in our class. The "getitem" method should return the item at the specified index when the object is indexed. For example, consider the following class:

class MyList:
    def __init__(self, items):
        self.items = items
    
    def __getitem__(self, index):
        return self.items[index]

>>> my_list = MyList([1, 2, 3, 4, 5])
>>> my_list[0]
1
>>> my_list[1:3]
[2, 3]

Here, we've defined a class "MyList" that takes a list of items as an argument. The "getitem" method simply returns the item at the specified index from the "items" list. Now, we can index and slice our "MyList" object just like we would with a built-in list.

In addition to indexing, we can also make our objects support slicing by implementing the "getitem" method to return a slice of the object. For example:

class MyList:
    def __init__(self, items):
        self.items = items
    
    def __getitem__(self, index):
        if isinstance(index, slice):
            start = index.start
            stop = index.stop
            step = index.step
            return self.items[start:stop:step]
        else:
            return self.items[index]

>>> my_list = MyList([1, 2, 3, 4, 5])
>>> my_list[0]
1
>>> my_list[
Another important aspect of subscriptable objects in Python is the "__setitem__" method. This method allows us to modify the elements of our objects using the square bracket notation. To implement the "__setitem__" method, we need to define it in our class and specify how the value should be updated at the specified index. Here's an example:

class MyList:
def init(self, items):
self.items = items

def __getitem__(self, index):
    if isinstance(index, slice):
        start = index.start
        stop = index.stop
        step = index.step
        return self.items[start:stop:step]
    else:
        return self.items[index]

def __setitem__(self, index, value):
    self.items[index] = value

my_list = MyList([1, 2, 3, 4, 5])
my_list[0] = 10
my_list.items
[10, 2, 3, 4, 5]

In the above example, we've added the "__setitem__" method to our "MyList" class. This method updates the value at the specified index in the "items" list.

Another important method to consider when creating subscriptable objects is the "__len__" method. This method should return the length of the object, and it is often used by functions such as "len" and "in". For example:

class MyList:
def init(self, items):
self.items = items

def __getitem__(self, index):
    if isinstance(index, slice):
        start = index.start
        stop = index.stop
        step = index.step
        return self.items[start:stop:step]
    else:
        return self.items[index]

def __setitem__(self, index, value):
    self.items[index] = value

def __len__(self):
    return len(self.items)

my_list = MyList([1, 2, 3, 4, 5])
len(my_list)
5

In the above example, we've added the "__len__" method to our "MyList" class. This method returns the length of the "items" list.

In conclusion, making objects subscriptable in Python involves implementing the "__getitem__" and "__setitem__" methods, as well as the "__len__" method for completeness. These methods allow us to use the square bracket notation to access and modify the elements of our objects, and make them more similar to built-in objects such as lists, tuples, and strings.
## Popular questions 
1. What is subscriptable in Python?
A: In Python, an object is considered subscriptable if it supports the square bracket notation for accessing and/or modifying its elements. This is achieved by implementing the "__getitem__" and/or "__setitem__" methods in the object's class.

2. What is the "__getitem__" method in Python?
A: The "__getitem__" method in Python is a special method that allows an object to be accessed using the square bracket notation. It returns the value at the specified index of the object. If the index is a slice, it returns a sub-sequence of the object.

3. What is the "__setitem__" method in Python?
A: The "__setitem__" method in Python is a special method that allows an object to be modified using the square bracket notation. It updates the value at the specified index of the object with a new value.

4. Why is the "__len__" method important for subscriptable objects in Python?
A: The "__len__" method in Python returns the length of an object, and is used by functions such as "len" and "in". When creating subscriptable objects, it is often a good idea to implement the "__len__" method to make the object more similar to built-in objects like lists, tuples, and strings.

5. Can you provide an example of a custom class that is subscriptable in Python?
A: Sure! Here's an example of a custom class "MyList" that is subscriptable in Python:

class MyList:
def init(self, items):
self.items = items

def __getitem__(self, index):
    if isinstance(index, slice):
        start = index.start
        stop = index.stop
        step = index.step
        return self.items[start:stop:step]
    else:
        return self.items[index]

def __setitem__(self, index, value):
    self.items[index] = value

def __len__(self):
    return len(self.items)

my_list = MyList([1, 2, 3, 4, 5])
my_list[0]
1
my_list[0] = 10
my_list[0]
10
len(my_list)
5

### Tag 
Subscripting.
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