Creating and Using Objects in Python: A Step-by-Step Guide

Rumman Ansari   Software Engineer   2024-07-26 02:27:46   650  Share
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Table of Content:

Creating Objects

  • An object is created by calling the class name followed by a pair of parenthesis.

class Person:             
    pass                    
p1 = Person()      # Creating the object 'p1'
print(p1)            # -> '<__main__.Person object at 0x0A...>'
  • The output of print on object p1, tell you what class it belongs to and hints on memory address it is referenced to.

Setting Attributes

  • You can set attributes, one a time, to an instantiated object and access it using the dot notation.

  • The value which is set to an attribute can be anything: a Python primitive, a built-in data type, another object. It can even be a function or a class.

Example


class Person:
    pass
p1 = Person()
p1.fname = 'Jack'
p1.lname = 'Simmons'
print(p1.fname, '-', p1.lname)  # -> 'Jack - Simmons'

Setting Attributes Contd..

  • You can also set multiple attributes, at once, by defining the initializer method, __init__, inside the class.

  • This method is called by default, during an object creation.

  • It takes values passed inside the parenthesis, during an object creation, as it's arguments.

  • It also takes self as the first argument, which refers to the current object.

Setting Attributes Example

  • In the following example, Person class sets two attributes using __init__ method.

class Person:
    def __init__(self, fname, lname):
        self.fname = fname
        self.lname = lname
p1 = Person('George', 'Smith')   
print(p1.fname, '-', p1.lname)           # -> 'George - Smith'

Documenting a Class

Each class or a method definition can have an optional first line, known as docstring.

Example


class Person:
    'Represents a person.'
    def __init__(self, fname, lname):
        'Initialises two attributes of a person.'
        self.fname = fname
        self.lname = lname

Understanding a Class

Once documented, you can load the script into an interactive interpreter and run help command on Person class.


 
>>>help(Person)

Help on class Person in module __main__:



class Person(builtins.object)

 |  Represents a person.

 |  

 |  Methods defined here:

 |  

 |  __init__(self, fname, lname)

 |      Initialises two attributes of a person.

 |  

... and more
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