How to print instances of a class using print()?

Question

I am learning the ropes in Python. When I try to print an object of class Foobar using the print() function, I get an output like this:

<__main__.Foobar instance at 0x7ff2a18c> 

Is there a way I can set the printing behaviour (or the string representation) of a class and its objects? For instance, when I call print() on a class object, I would like to print its data members in a certain format. How to achieve this in Python?

If you are familiar with C++ classes, the above can be achieved for the standard ostream by adding a friend ostream& operator << (ostream&, const Foobar&) method for the class.

Answer 1

>>> class Test: ...     def __repr__(self): ...         return "Test()" ...     def __str__(self): ...         return "member of Test" ...  >>> t = Test() >>> t Test() >>> print(t) member of Test 

The __str__ method is what gets called happens when you print it, and the __repr__ method is what happens when you use the repr() function (or when you look at it with the interactive prompt).

If no __str__ method is given, Python will print the result of __repr__ instead. If you define __str__ but not __repr__, Python will use what you see above as the __repr__, but still use __str__ for printing.