In this blog, we will learn everything about __str__ python function. We will understand the __str__ python function with multiple examples. so let’s get started.
what is __str__ function in python
The __str__ method is a special method in Python classes that is used to define a string representation of an object. The method should return a string that provides a human-readable representation of the object’s state. This string is used when the object is printed, or when the built-in str() function is called on the object.
If the __str__ method is not defined for a class, the interpreter will use the default implementation, which returns the name of the object’s class and its memory address.
Syntax of __str__ python function
The syntax for the __str__ method in a Python class is as follows:
class MyClass:
def __init__(self, ...):
# Initialization code
def __str__(self):
return "string representation of the object"The method should be defined within the class and should be named __str__. It should not take any arguments and it should return a string.
How to call a __str__ function in python
In Python, the __str__ method is called automatically when an object is used in a string context, such as when it is printed, or when the built-in str() function is called on the object.
For example, consider the following class My_person_class with an __str__ method defined:
class My_person_class:
def __init__(self, name, city, age):
self.name = name
self.city = city
self.age = age
def __str__(self):
return f"{self.name} who lives in {self.city} is {self.age} years old"
person1 = My_person_class("Tom","USA", 30)
print(person1)The above code will create an instance of the class My_person_class called person1 with the name “Tom”, city “USA”, and age 30. And then when you print person1, the __str__ method will be called automatically and it will return a string representation of the object
Also, you can test it by calling str(person1) function, it will return the same string representation of the object.
print(str(person1))
__str__ python example
Below is an example of how the __str__ method can be used in a Python class.
class My_book:
def __init__(self, title, author, pages):
self.title = title
self.author = author
self.pages = pages
def __str__(self):
return f"Book {self.title} is written by {self.author} have {self.pages} pages"
book1 = My_book("Moby-Dick", "Herman Melville", 635)
print(book1)
print(str(book1))If you run the above code, it will create an instance of the class My_book called book1 with the title “Moby-Dick”, author “Herman Melville”, and 635 pages. And then when you print book1, the __str__ method will be called automatically and it will return a string representation of the object:
__str__ vs __repr__ function in python
In Python, the __str__ and __repr__ methods are used to define string representations of an object. The main difference between the two is their intended use and audience.
- The
__str__method is used to define a string representation of an object that is intended for end-users.On the other hand, the__repr__method is used to define a string representation of an object that is intended for developers. - _str__ return a string that provides a human-readable representation of the object’s state whereas __repr__ return a string that provides an unambiguous representation of the object’s state.
- __str__ string is used when the object is printed, or when the built-in
str()function is called on the object whereas __repr__ is used when the object is printed in the interpreter, or when the built-inrepr()function is called on the object. - If the
__str__method is not defined for a class, the interpreter will fall back to using the__repr__method and if the__repr__method is also not defined, the interpreter will use the default implementation. - Below is an example of how the
__str__and__repr__methods can be used in a Python class
class My_book:
def __init__(self, title, author, pages):
self.title = title
self.author = author
self.pages = pages
def __str__(self):
return f"Book {self.title} is written by {self.author} have {self.pages} pages"
def __repr__(self):
return f"Book('{self.title}', '{self.author}', {self.pages})"
book1 = My_book("Moby-Dick", "Herman Melville", 635)
print(book1)
print(str(book1))
print(repr(book1))the above code, it will create an instance of the class My_book called book1 with the title “Moby-Dick”, author “Herman Melville”, and 635 pages. And then when you print book1, the __str__ method will be called automatically and it will return a string representation of the object
Book Moby-Dick is written by Herman Melville have 635 pages
And when you call str(book1) it will return the same string representation of the object as print(book1)
Book Moby-Dick is written by Herman Melville have 635 pages
And when you call repr(book1) it will return a string that provides an unambiguous representation of the object’s state, this string is used when the object is printed in the interpreter, or when the built-in repr() function is called on the object.
Book('Moby-Dick', 'Herman Melville', 635)Conclusion
I hope you have liked this detailed tutorial on the __str__ python function. Please do let me know if you are facing any issues.
