Constructor parameters in Python - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a constructor in Python?

A constructor is a special method named __init__ that runs automatically when you create a new object from a class. It sets up the object’s initial state.

beginner

How do constructor parameters help when creating an object?

Constructor parameters let you give values to the object right when you create it. This way, each object can start with its own unique data.

beginner

What does this code do?<br><pre>class Car:
    def __init__(self, color):
        self.color = color

my_car = Car('red')</pre>

This code defines a class Car with a constructor that takes a color parameter. When my_car is created, it sets its color to 'red'.

intermediate

Can constructor parameters have default values? How?

Yes! You can give constructor parameters default values by assigning them in the __init__ method, like def __init__(self, color='blue'):. If no value is given, the default is used.

beginner

Why do we use self in constructor parameters?

self represents the object being created. It lets us store the parameter values inside the object so they can be used later.

What is the name of the constructor method in Python?

A __start__

B __init__

C constructor

D init

The constructor method in Python is always named __init__.

What does the self parameter represent in a constructor?

A The object being created

B The class itself

C A global variable

D A function parameter unrelated to the object

self refers to the specific object being created or used.

How can you give a constructor parameter a default value?

A By calling a separate method

B By setting it outside the class

C By using a global variable

D By assigning a value in the parameter list, e.g., <code>def __init__(self, x=5):</code>

Default values are set by assigning them in the parameter list of the constructor.

What happens if you create an object without passing a required constructor parameter?

A Python raises an error

B The object is created with default values

C The parameter is set to None automatically

D The program ignores the missing parameter

If a required parameter is missing, Python raises a TypeError.

Why do we assign constructor parameters to self attributes?

A To make the parameters global

B To delete the parameters after use

C To save the values inside the object for later use

D To print the values immediately

Assigning to self stores the values inside the object so they can be accessed anytime.

Explain what constructor parameters are and why they are useful.

Think about how you give information to a new object when you create it.

Describe the role of self in a constructor and how it relates to parameters.

Consider how the object keeps its own information.