repr and str

Let's explore some of the most useful magic methods.

We're already familiar with the __init__ magic method, which we considered earlier. However, there are many other magic methods that can be incredibly useful. In this section, we'll focus on two of them: __repr__ and __str__.

Class Representation

When you create an instance of your class and try to print it in the console, you may encounter a representation that may not be very informative or user-friendly:


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class User:
    def __init__(self, username):
        self.username = username

instance = User("top.user.123")

print(instance)

To obtain a more understandable and informative output when printing an instance, you can define the __repr__ magic method, which stands for "representation".


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class User:
    def __init__(self, username):
        self.username = username

    def __repr__(self):
        return f"User: {self.username}"

instance = User("top.user.123")

print(instance)

The provided code defines a class called User. The User class includes a magic method __repr__, which returns a string representation of the object. In this case, the __repr__ method returns a formatted string that includes the class name "User" and the value of the username attribute.

When the print statement is executed, it calls the __repr__ method of the instance object to obtain a string representation of the object. In this case, the __repr__ method is overridden in the User class to provide a custom representation.

String Representation

The __str__ magic method functions similarly to __repr__, but it is specifically used to provide information and a more readable representation of an object to users.


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class User:
    def __init__(self, username):
        self.username = username

    def __repr__(self):
        return f"User: {self.username}"

    def __str__(self):
        return f"This is a user {self.username}"

instance = User("top.user.123")

print(instance)

The print() function searches for the __str__ magic method in an object to obtain a string representation. If the __str__ method is not defined, it falls back to using the __repr__ method.

Additionally, the __str__ magic method can be used to convert an instance to a string type explicitly. By implementing the __str__ method, you can define how the object should be represented as a string.


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class User:
    def __init__(self, username):
        self.username = username

    def __repr__(self):
        return f"User: {self.username}"

    def __str__(self):
        return f"{self.username}"

instance = User("top.user.123")
string = str(instance) + " is the best user!"

print(string)

Note

In summary, the __str__ and __repr__ magic methods are used to define different string representations of objects in Python. The __str__ method is typically used to provide a user-friendly output, presenting the object in a way that is easy to understand for users. On the other hand, the __repr__ method is used to provide a developer-friendly output, typically containing more detailed information about the object for debugging and internal use.

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