String representation methods in Python - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is the purpose of the __str__ method in a Python class?

The __str__ method defines the "informal" or nicely printable string representation of an object. It is used by the print() function and str() to show a user-friendly description.

beginner

What does the __repr__ method do in Python?

The __repr__ method returns an "official" string representation of an object. It is meant to be unambiguous and, if possible, match the code needed to recreate the object. Used by repr() and in the interactive interpreter.

intermediate

If a class has both <code>__str__</code> and <code>__repr__</code> methods, which one does <code>print()</code> use?

print() uses the __str__ method if it is defined. If __str__ is missing, it falls back to __repr__.

intermediate

Write a simple Python class Person with __str__ and __repr__ methods that show the person's name and age.

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})"

intermediate

Why is it recommended that __repr__ returns a string that could be used to recreate the object?

Because __repr__ is mainly for developers, returning a string that can recreate the object helps debugging and testing. It shows the object's details clearly and can be used with eval() to make a copy.

Which method is called by the print() function to get an object's string representation?

A __del__

B __repr__

C __init__

D __str__

print() uses the __str__ method if available to show a user-friendly string.

What is the main difference between __str__ and __repr__?

A __str__ is for users; __repr__ is for developers

B __repr__ is for users; __str__ is for developers

C Both are exactly the same

D __str__ is only for numbers

__str__ gives a readable string for users; __repr__ gives a detailed string for developers.

If a class defines only __repr__ but not __str__, what happens when you use print() on its object?

A It prints nothing

B It raises an error

C It uses __repr__ output

D It uses __init__ output

If __str__ is missing, print() falls back to __repr__.

Which of these is a good practice for __repr__?

A Return a string that can recreate the object

B Return a short emoji

C Return an empty string

D Return a random number

__repr__ should return a string that looks like the code to recreate the object.

What happens if neither __str__ nor __repr__ is defined in a class?

A Python crashes

B Python shows a default string like <ClassName object at memory_address>

C Python prints None

D Python prints an empty line

Python uses a default representation showing the class name and memory address.

Explain the difference between the __str__ and __repr__ methods in Python classes.

Think about who sees the output: users or developers.

Write a Python class with both __str__ and __repr__ methods and describe what each returns.

Use a simple example like a Person with name and age.