How to Make Custom Class Printable in Python Easily

To make a custom class printable in Python, define the __str__ method to return a user-friendly string representation. Optionally, define __repr__ for an unambiguous representation useful for debugging.

Syntax

Define the __str__ method inside your class to control what is shown when you print an object. Optionally, define __repr__ to provide a detailed string for debugging.

• def __str__(self): returns a readable string.
• def __repr__(self): returns a detailed string for developers.

python

class ClassName:
    def __str__(self):
        return "User-friendly string"

    def __repr__(self):
        return "Detailed representation for debugging"

Example

This example shows a Person class with __str__ and __repr__ methods. Printing the object calls __str__, while just typing the object in the console calls __repr__.

python

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

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

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

p = Person("Alice", 30)
print(p)
p

Output

Person named Alice, aged 30
Person(name='Alice', age=30)

Common Pitfalls

Many beginners forget to define __str__, so printing the object shows a default message like <__main__.ClassName object at 0x...>. Also, confusing __str__ and __repr__ can lead to unclear outputs.

Always define __str__ for user-friendly output and __repr__ for debugging.

python

class Wrong:
    pass

w = Wrong()
print(w)  # Output is not helpful

class Right:
    def __str__(self):
        return "Nice output"

r = Right()
print(r)  # Output is nice

Output

<__main__.Wrong object at 0x7f...>
Nice output

Quick Reference

Summary tips:

• __str__ controls print() output.
• __repr__ controls interactive console output.
• Use !r in f-strings inside __repr__ for quotes.
• Always return strings from these methods.

Key Takeaways

Define __str__ to customize what print() shows for your class objects.

Define __repr__ to provide a clear, unambiguous string useful for debugging.

If __str__ is missing, print() shows a default, less helpful message.

Use f-strings with !r in __repr__ to show quotes around strings.

Always return strings from __str__ and __repr__ methods.