How to print objects of class using print function in Python

Question

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

<__main__.Foobar instance at 0x7ff2a18c>

For instance, when I call print() on a class object, I would like to print its data members in a certain format that is easy to grasp.

How to achieve this easily in Python? Appreciate some help.

Answer 1

It can be done as shown below:

class Element:
    def __init__(self, name, symbol, number):
        self.name = name
        self.symbol = symbol
        self.number = number

    def __str__(self):
        return str(self.__class__) + ": " + str(self.__dict__)

And then,

elem = Element('my_name', 'some_symbol', 3)
print(elem)

produces

__main__.Element: {'symbol': 'some_symbol', 'name': 'my_name', 'number': 3}

Hope this helps!

If you are a beginner and need to know more about Python, It's recommended to go for Python Certification course today.

Thanks!

Answer 2

print(a.__dict__)

Just replace the A with "Foobar" or whatever else you want...

Answer 3

Printing objects give us information about the objects we are working with. In C++, we can do this by adding a friend ostream& operator << (ostream&, const Foobar&) method for the class. In Java, we use toString() method. In Python, this can be achieved by using __repr__ or __str__ methods.

Answer 4

>>> 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 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 this isn't the most Pythonic method, I apologize, because I'm still learning too - but it works.

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.