How do you Convert a String to a Python Class Object?

A class is defined as a storage of variables of an instance, and a class is a method that is used to specify an object type. A class can be used to make as many instances of objects of the type of object that are needed. An object is an identified entity with some attributes that are also called data members and behaviors, also called member functions. A group of objects that share similar characteristics and behavior is an instance of the same class. A class is a prototype that is user-defined, and with the help of classes, objects are created. A new type of object is created by creating a new class that allows instances of that type to be made. Each class can have attributes attached to it to maintain its state. Consider an example: you want to keep the number of dogs that may contain different attributes like breed and age. If we use a list to track the number of dogs, then the first element could be a dog's breed, and the second element could be the age. But what if there are 100 different dogs? Then how do we know which element is supposed to be which? What other properties do you want to add to these dogs? This lacks organization, and it's the exact need for classes.

Syntax for Defining a Class:

class is a keyword in Python that is used to define the class.

Syntax for Defining an Object:

The class can be called the user-defined data structure that holds its own data members and member functions, which can be accessed and can be used by creating an instance.

Some Key Points on Python Class:

• Classes are declared by class keyword.
• The variables that belong to the class are called attributes.
• Attributes are always public and can be accessed with the help of a dot (.)

Creating a class in Python:

Code:

The class is created with the help of the class keyword, and the name of the class is a dog.

The Object of the Python Class:

An object is an instance of class. A class is like a blueprint, while an object is an instance that is a copy of the class with original values.

An object contains:

• State: The attribute of an object that also shows the properties of an object.
• Behavior: The method of an object that also shows the response of an object to other objects.
• Identity: It gives a distinct name to an object and enables one object to interact with other objects.

Declaring Class Objects (Also called Instantiating a Class):

When an object in class is created, the class is referred to as instantiated. All the instances share the attributes and the behavior of the class. However, the values of the attributes are distinct from each other. A single class may contain many instances.

Example of Python Class and object:

To create an object in Python, we first have to create a class and instantiate a class to create a new instance for the class that we create. This process is called object instantiation.

Code:

Output:

mammal
I'm a mammal
I'm a dog

Explanation:

In the class Dog, we create an object that is basically a Dog named bull_dog. This class has only two class attributes, telling us that bull_dog is a dog and a mammal. We have two class variables, attr1 and attr2. A method is created with the name fun () that returns the string "I'm a, {attr1}" and "I'm a, {attr2}". An object of the dog class is created, and the attr1 of the object is printed. In the end, the fun () function is called.

Self Parameter:

A method is called the object as my object.method (arg1, arg2), which is automatically converted by Python into MyClass.method (myobject, arg1, arg2).

Code

Output:

Hello, my name is John, and I work in Dev.

The parameter self in the init function is not call itself, instead of it you can use any other name.

String In Python:

It is a sequence of characters. If you want to enter a text in Python, it is stored as a string. You can use strings in Python as follows:

• Using single quotes: You can write a string using single quotes, for example: 'javatpoint.'
• Using double quotes: You can also write strings using double quotes, such as "javatpoint."
• Using triple quotes(''' '''): Using triple quotes for writing a string allows you to write multiple lines in Python.

We can use operations like addition and multiplication on strings. The addition of two strings is known as concatenation. For example: "Python " + "Programming" is printed as Python Programming, and 'Python'*2 is printed as PythonPython. The Python string is represented by the str class. Operations that can be performed on the strings are concatenation, slicing, and repetition.

Code:

Output:

Hello, welcome to the world of Python programming
<class 'str'>
Python Programming

Explanation:

In the above code, a string is input with the value Hello, welcome to the world of Python programming in the single quotes, and the string is printed, and the type of the string is also printed, which is the class string. In the last print statement, the strings are concatenated.

Let's see how to convert a string to a Python object:

The string can be converted to a Python object with the help of many methods depending on the type of object that should be created. There are various common methods that are given below:

1. 'eval()' function: The eval() method is used to find the expression in the string, and the result is returned. It is very important to note that when the eval function is used, it can execute arbitrary code and might be a security risk if the string comes from an untrusted source.

Code:

Output:

7

Explanation:

In the above code, the expression is input '3 + 4' when passed to the eval function the result is printed as the sum of two numbers that is 7.

2. 'ast.literal_eval()': This function is used to evaluate the expression that contains literals (strings, numbers, tuples, lists, dicts, Booleans, and None) without running any code:

Code:

Output:

[1,2,3]

Explanation:

In the above code, the ast module is imported, and the string of the list is input and with the help of ast.literal_eval function, the string is evaluated as a list.

3. 'json.load()': This function is used to represent a JSON object, the json.loads() function is used to parse it into a Python object.

Code:

Output:

{'name': 'John', 'age': 30}

Explanation:

In the above code, json module is imported, and a string is input as a json object with the help of json.loads method, the result is obtained as a json object.

4. Custom Parsing: If the string need to be follow a specific format and none of the above methods suit the requirements then a custom parsing can be written for the string to convert to the object.