Question

I really don’t understand where are __str__ and __repr__ used in Python. I mean, I get that __str__ returns the string representation of an object. But why would I need that? In what use case scenario? Also, I read about the usage of __repr__

But what I don’t understand is, where would I use them?

Answer 1

__repr__

Called by the repr() built-in function and by string conversions (reverse quotes) to compute the “official” string representation of an object. If at all possible, this should look like a valid Python expression that could be used to recreate an object with the same value (given an appropriate environment).

__str__

Called by the str() built-in function and by the print statement to compute the “informal” string representation of an object.

Use __str__ if you have a class, and you’ll want an informative/informal output, whenever you use this object as part of string. E.g. you can define __str__ methods for Django models, which then gets rendered in the Django administration interface. Instead of something like <Model object> you’ll get like first and last name of a person, the name and date of an event, etc.

---

__repr__ and __str__ are similar, in fact sometimes equal (Example from BaseSet class in sets.py from the standard library):

def __repr__(self):
    """Return string representation of a set.

    This looks like 'Set([<list of elements>])'.
    """
    return self._repr()

# __str__ is the same as __repr__
__str__ = __repr__