How to Override `__str__` and `__repr__` for Customized Print Output of Class Instances?

How to Customize the String Representation of Class Instances with print()

When printing instances of a class, the default behavior often displays the memory location of the object. To customize the string representation and control what is shown when printing, you can implement two special methods: str and __repr__.

__str__: Defining the Human-Readable String Representation

The str method defines the string representation of an object for general use. It is invoked when you call print() or str() on the object. By overriding __str__, you can define the custom output that is displayed when printing.

__repr__: Defining the String Representation for Debugging

The repr method defines the string representation intended for debugging purposes. It is invoked when you call repr() on the object or if you do not define str__. The __repr representation should be a valid Python expression that evaluates to the object.

Example

To customize the string representation of your class instances:

class Test:
    def __init__(self):
        self.a = 'foo'

    def __str__(self):
        return "member of Test"

    def __repr__(self):
        return "Test()"

In the example above:

• The str method returns a human-readable string, "member of Test", when you print the object.
• The repr method returns a valid Python expression, "Test()", that would recreate the object.

When you print an instance of this class:

t = Test()
print(t)

It will display "member of Test" on the console, providing a custom and meaningful representation.

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