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Learn to program with Python

Change message when an object is printed #

Now that we have our own MyStr class, let's see the difference between when MyStr and str objects are printed.

normal_str = str("Python is awesome!")
print(normal_str) # Output: Python is awesome!

my_str = MyStr("Python is awesome!")
print(my_str) # <__main__.MyStr object at 0x7fd0908896c0>

When MyStr object is printed, the message displays the type of the object, along with the position in the memory, which isn't very useful. We want the message to be the same as str object.

Special method: __str__ #

The __str__ method is a special method that provides a string representation of an object. It is called by the built-in str() function and the print() function when attempting to convert an object to a string.

For example:

class Dog:
    def __init__(self, name):
        self.name = name

    def __str__(self):
        return f"This is a dog named {self.name}"

max_the_dog = Dog("Max")
print(max_the_dog) # This is a dog named Max

In the example above, we create a new class, Dog, which accepts an argument when constructed. The value of name is then set as an object property, conveniently named name. We then defined the method __str__, which returns a string to be the message when a Dog object is printed.

Now that we know how to use the method __str__, let's implement it in our MyStr class.

Exercise #

  • Update the __init__ method to set the property text in our MyStr class and implement the __str__ method to return the value of text property.

Tests #

  • MyStr("Python is awesome") should create an object with following attributes:
    • Property text should be "Python is awesome!"
  • MyStr("Programming is fun") should create an object with following attributes:
    • Property text should be "Programming is fun"
  • print(MyStr("Python is awesome!")) should print the message "Python is awesome!"
Output will be displayed here