Intro to Python: Day 15 - OOP - Overriding the Print Method on a Custom Class

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So every programming language has its own built-in behavior for printing different kinds of objects. In Python, if you have a custom class, printing an instance of the class will simply print a pointer which indicates its place in your storage. It's pretty useless.

class Animal():
    def __init__(self, type):
        self.type = type

lion = Animal("lion") 

print(lion)

# prints "<Lion object at 0xa0acf8>"

(Note: This example is adapted from the super duper helpful OOP course at dev.to)

So, if we want to override the built-in print functionality, all we need to do is specify it using the built-in instance method __str__().

class Animal():
    def __init__(self, type):
        self.type = type

    def __str__(self):
        return f"I am a {self.type} type of animal."

lion = Animal("lion") 

print(lion)

# prints "I am a lion type of animal."

Pretty cool eh? If you're working extensively with custom classes, having them be able to show useful information when printed can be useful.

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