What is the difference between __str__ and __repr__ in Python?

In Python, both __str__ and __repr__ are special methods used to provide string representations of objects. The __str__ method is used for creating user-friendly, human-readable string representations. It is typically used for displaying the object to end-users. On the other hand, the __repr__ method is used to provide a detailed, unambiguous representation of the object. It is mainly used for debugging purposes and should ideally be a valid Python expression that can recreate the object. If __str__ is not defined, Python falls back to using __repr__.

Code Example

class Person:
    def __init__(self, name, age):
        self.name = name
        self.age = age

    def __str__(self):
        return f"Person(name={self.name}, age={self.age})"

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

person = Person("Alice", 25)

# Using str()
print(str(person))

# Using repr()
print(repr(person))

Output

Person(name=Alice, age=25)
Person(name='Alice', age=25)

Code Explanation

In this example, we define a Person class with two attributes: name and age. The class has two special methods: __str__ and __repr__.

The __str__ method is called by the built-in str() function and provides a human-readable string representation of the object. It is intended for end-users to understand and display the object. In this example, __str__ returns a formatted string that includes the name and age of the person.

The __repr__ method is called by the built-in repr() function and provides an unambiguous string representation of the object. It is mainly used for debugging purposes and should ideally be a valid Python expression that can recreate the object. In this example, __repr__ returns a string representation that includes the name and age of the person, enclosed in quotes.

When we create an instance of the Person class and print it using str(person), it calls the __str__ method and returns a user-friendly string representation, "Person(name=Alice, age=25)". The __str__ method is used to provide a more readable representation for the end-user.

On the other hand, when we print the object using repr(person), it calls the __repr__ method and returns an unambiguous string representation, "Person(name='Alice', age=25)". The __repr__ method provides a detailed representation that includes the actual Python expression to recreate the object.

By implementing both __str__ and __repr__ methods in a class, you can control how the object is displayed in different contexts, providing more meaningful output for users and more detailed information for debugging purposes.