Python __repr__

How repr() Works in Python?

The repr() function in Python calls an object’s __repr__() method to obtain its string representation. For built-in types, Python provides a default __repr__ implementation that outputs a developer-friendly, unambiguous representation of the object. For user-defined classes, you can override the __repr__ method to customize the output.

Example 1: Using repr() with Built-in Types      

• Python

Python

# Using repr() with different objects
print(repr(123))              
print(repr(3.14))            
print(repr("Hello, world!"))  
print(repr([1, 2, 3]))  

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Output:

'123'
'3.14'
"'Hello, world!'"
'[1, 2, 3]'

Example 2: Using repr() with User-defined Classes

• Python

Python

class Person:
    def __init__(self, name, age):
        self.name = name
        self.age = age
    
    def __repr__(self):
        return f"Person(name='{self.name}', age={self.age})"

# Create an instance of Person
person = Person("Rahul", 30)

# Use repr()
print(repr(person))  

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Output:

Person(name='Rahul', age=30)

Python __repr__ Implementation

In this section of the article “Python __repr__”, we will see the implementation of the __repr__() method.

Example 1

In this example, we will implement __repr__ in python by creating a class “Car”.

Code

• Python

Python

# Creating class "Car"
class Car:

    # Creating __init__ method to initialize the instance variables
    def __init__(self, name, model):
        self.name = name
        self.model = model
       
    # Creating __repr__ method to represent the object of class "Car"
    def __repr__(self):
        rep = 'Car(' + self.name + ', ' + self.model + ')'
        return rep

# Creating the objects "car1" and "car2" of class "Car"
car1 = Car("BMW", "i7")
car2 = Car("Mercedes", "S-Class")

# Representation of objects "car1" and "car2" by printing them using repr() method
print(repr(car1))
print(repr(car2))

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Output

Explanation

In the above code, we created a class called “Car”, in which two magic methods are present. One magic method is the __init__() method, which will be called automatically for the initialization. The second magic method is __repr__() method which is called for the representation of the object of this class, there is a string returned as the result of this method. After that, two objects are created whose names are “car1” and “car2”, which is then passed to the repr() method, and the printing is done.

Example 2

Let's take one more example to understand better In this example, we will create a class called “College”, where we will represent its object using the __repr__ method. Here is the code for the same:

Code

• Python

Python

# Creating class "College"

class College:

    # Creating __init__ method to initialize the instance variables

    def __init__(self, name, country, salary):

        self.name = name

        self.country = country

        self.salary = salary

    # Creating __repr__ method to represent the object of class "College"

    def __repr__(self):

        return str(self.name)+' | '+str(self.country)+' | '+str(self.salary)

# Creating the objects "clg1", "clg2" and "clg3" of class "Collge"

clg1 = College("IIT Delhi", "India", "17 LPA")

clg2 = College("IIT Bombay", "India", "20 LPA")

clg3 = College("IIM Bangalore", "India", "23 LPA")

# Representation of objects "car1", "car2" and "car3" by printing them using repr() method

print(repr(clg1))

print(repr(clg2))

print(repr(clg3))

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Output

Explanation

In the above code, we created a class called “College”, in which two magic methods are present. One magic method is the __init__() method, which will be called automatically for the initialization. The second magic method is __repr__() method which is called for the representation of the object of this class, there is a string returned as the result of this method. After that, three objects are created whose names are “clg1”, “clg2”, and “clg3”, which is then passed to the repr() method, and the printing is done.

Magic Methods

Magic Methods, also known as Dunder methods, contain two underscores in the prefix and suffix, and Dunder means Double Underscores. Few types of magic methods are: 

• __init__() method: There are constructors in several languages such as C++, C#, and Java. Similarly, this method used for initialization without any call.
   
• __add__() method: It is a magic method that is used to add two objects that returns the third object.
   
• __len__() method: It is a magic method that is used to determine the length of objects passed to this method.
   
• __repr__() method: This method is used to represent a class’s objects and returns a string

Frequently Asked Questions

How __repr__ can be used for logging and debugging?

If there are any errors in the application created using Python, then the __repr__ method can be used to print the error or meaningful message about the object.

How __repr__ can be used for serializing and deserializing?

The __repr__ method can be used for converting objects to JSON or XML and converting them back to objects which are known as serializing and deserializing.

What does repr mean?

repr stands for "representation." It provides an unambiguous string representation of an object, useful for debugging and logging, often invoking __repr__().

What is __repr__ and __str__ in Python?

__repr__ provides a developer-friendly representation, while __str__ provides a user-friendly one. repr() calls __repr__, and str() or print() calls __str__.

Does print use __repr__ or __str__?

print() uses __str__ if available; otherwise, it defaults to __repr__. The goal is to display a readable string for users.

Conclusion

Magic Methods, also known as Dunder methods, contain two underscores in the prefix and suffix. Here __repr__ method is one of the magic methods that can be used to represent the class’s object. 

In this article, we discussed what are the magic methods, and we also discussed one of the magic methods called __repr__ along with its implementation. Here are more articles that are recommended to read:

• Methods of Dictionary
• Functions in Python
• Objects and Classes in Python
• Object-Oriented Programming Python
• Python packages
   

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