How Can I Customize the String Representation of My Python Class Instances?

Custom String Representation for Class Instances

When printing instances of a class, the default output often provides only the class name and an object address. To customize this output and display specific attributes, one can define the string representation of the class.

Using str and repr Methods

Python provides two special methods, str and __repr__, that control the string representation of an object. By overriding these methods within a class, one can specify how instances of the class should appear when printed.

str Method

The str method defines the string representation to be displayed when the print function is used. It should return a string representation of the object. For example:

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

repr Method

The repr method defines the string representation to be displayed when the repr() function is used or the object is inspected in the interactive prompt. It should return a string representation that can be used to recreate the object. For example:

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

Example

Consider the following example:

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

    def __str__(self):
        return str(self.a)

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

When printing an instance of this class, the following outputs will be displayed:

>>> print(Test())
foo

>>> repr(Test())
Test()

By defining both the str and repr methods, you have complete control over the string representation of your class instances.

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