Python - Method

Method

What is method?

A Python method is a label that you can call on an object; it is a piece of code to execute on that object. ^[1]

The difference between method and function

A method in python is similar to a function, except it is associated with object/classes. There are two major differences. ^[2]

• The method is implicitly used for an object for which it is called.

• The method is accessible to data that is contained within the class.

class Pet(object):
    def my_method(self):
        print("I am a Cat")
cat = Pet()
cat.my_method()

>> I am a Cat

If we want object accept arguments, like

cat = Pet('Cat')

We need __init__ method. Otherwise, the program will report error as “TypeError: object() takes no arguments.”

The __init__ method lets us assign a value for the “self.name” variable in our class. Here the __init__ is one way to implement magic method in python.

class Pet:
    def __init__(self, name):
        self.name = name
    def my_method(self):
        print(f"I am a {self.name}")
cat = Pet("Cat")
cat.my_method()

>> I am a Cat

##Class
A Class is like an object constructor, or a “blueprint” for creating objects. ^[3]

It has all the properties mentioned in the plan, and the corresponding object behaves as the plan.

We can take a the class ‘Student’ as example. It contains properties like name, gender, and grade.

class Student:
    def __init__(self, name, gender, score):
        self.name = name
        self.gender = gender
        self.score = score
    def grade(self):
        if self.score>=60:
            print(f'{self.name} passes the final exam.')
        else:
            print(f'{self.name} fails the final exam.')

student1 = Student(name = 'Arwen', gender = 'female', score = 80)

##Object
A Python object is an instance of a class. It can have properties and behavior accordingly. We just created the class “Student” and an object “student1”. So we can access the method and the attribute of “student1”:

student1.grade()

Arwen passes the final exam.

student1.gender

>> 'female'

We can use other magic method in python, such as __dict__. ^[4]

For class “Student”, __dict__ returns all the attributes in the class.

Student.__dict__

>> mappingproxy({'__module__': '__main__',
>>               '__init__': <function __main__.Student.__init__(self, name, gender, score)>,
>>              'grade': <function __main__.Student.grade(self)>,
>>               '__dict__': <attribute '__dict__' of 'Student' objects>,
>>              '__weakref__': <attribute '__weakref__' of 'Student' objects>,
>>               '__doc__': None})

For object “student1”, __dict__ returns all the attributes of the object. The method in the class will not be included.

student1.__dict

>> {'name': 'Arwen', 'gender': 'female', 'score': 80}

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1. Python Method – Classes, Objects and Functions in Python ↩
2. Difference between Method and Function in Python ↩
3. Python Classes and Objects ↩
4. dict attribute and vars() function in python. ↩
5. Python magic methods ↩