The __repr__ method

__repr__(self)

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). If this is not possible, a string of the form “<…some useful description…>” should be returned. The return value must be a string object. If a class defines __repr__ but not __str__, then __repr__ is also used when an informal string representation of instances of that class is required.

This is typically used for debugging, so it is important that the representation is information-rich and unambiguous.