This is a 100 Days challenge to learn a new language (Python). 100 Days of Code - The Complete Python Pro Bootcamp
I will post some notes to motivate myself to finish this challenge.
How to create a class
Class is a Blueprint.
It starts with 'class' keyword, followed with class name.
Ex:
# Define a class
class User:
# pass statement
pass
# Use class to create an object
user = User()
Naming Convention
camelCase (helloWorld)
Used it in Python only if needed (backwards compatibility). Reference
What is pass statement
Under 'How to create a class' section, what will it happen if we remove pass statement?
# Define a class
class User:
# pass statement
# pass
# Use class to create an object
user = User()
Error:
user_1 = User()
^
IndentationError: expected an indented blockIn python, empty code is not allowed in loops, function, class, and if else condition.
Therefore, you will get an error if you run previous example since interpreter think you forget to give them some indents.
The solution is to add pass statement. 'pass' statement is used as a placeholder for future code.
Also, note that interpreter will ignore comments totally, but 'pass' is not ignored.
Constructor
We can setup attributes of object after creating. This way is error prone because we might have typo.
Ex (Without Constructor):
# Define a Class without Constructor
class User:
pass
# Using Class to create an object
user = User()
# set object attribute 'id' to 001
user.id = "001"
# if we have a typo (change i to l) from the previous instruction
# then user.id will not be setup
# and it is hard to debug
# user.ld = "001"
print(f"user id: { user.id}")
Constructor is also called initializer.
The recommended way to use.
Ex:
# Define a Class
class User:
# Constructor
def __init__(self, id):
self.id = id
# Using Class to create an object
user = User(1)
print(f"user id: {user.id}")
Then we just need to pass parameters to Class when creating.
What is 'self' in constructor?
self represents the instance of the class.
By using the 'self' keyword we can access the attributes and methods of the class in python.
Adding methods
Ex:
# Define a class
class User:
# Constructor
# Init attributes
def __init__(self, user_id, username):
self.id = user_id
self.username = username
self.followers = 0
self.following = 0
# Methods
def follow(self, user):
user.followers += 1
self.following += 1
# Create objects
user_1 = User("001", "Frank")
user_2 = User("002", "Jake")
user_3 = User("003", "Mary")
# Call methods
user_2.follow(user_1)
user_3.follow(user_1)
print(
f"user 1: {user_1.id} - {user_1.username} -
{user_1.followers} - {user_1.following}"
)
print(
f"user 2: {user_2.id} - {user_2.username} -
{user_2.followers} - {user_2.following}"
)
print(
f"user 3: {user_3.id} - {user_3.username} -
{user_3.followers} - {user_3.following}"
)
Result:
user 1: 001 - Frank - 2 - 0
user 2: 002 - Jake - 0 - 1
user 3: 003 - Mary - 0 - 1Challenge - Build a Quiz Project
Build a quiz project with OOP style.
* Question class:
attributes
text
answer
* QuizBrain class
attributes
score
question_number
question_list
methods
still_has_questions
next_question
check_answer
Ex:
data.py (Quiz Resource)
question_data = [
{
"category": "Entertainment: Video Games",
"type": "boolean",
"difficulty": "easy",
"question": "Peter Molyneux was the founder of Bullfrog
Productions.",
"correct_answer": "True",
"incorrect_answers": ["False"],
},
{
"category": "Vehicles",
"type": "boolean",
"difficulty": "hard",
"question": "In 1993 Swedish car manufacturer Saab experimented
with replacing the steering wheel
with a joystick in a Saab 9000.",
"correct_answer": "True",
"incorrect_answers": ["False"],
},
{
"category": "General Knowledge",
"type": "boolean",
"difficulty": "easy",
"question": "French is an official language in Canada.",
"correct_answer": "True",
"incorrect_answers": ["False"],
},
]
question_model.py
class Question:
"""Question"""
def __init__(self, text, answer):
self.text = text
self.answer = answer
question_model.py
class QuizBrain:
"""QuizBrain"""
# Constructor
def __init__(self, question_list):
self.question_list = question_list
self.score = 0
self.question_number = 0
def still_has_questions(self):
if self.question_number >= len(self.question_list):
return False
return True
def next_question(self):
# Increase question number
self.question_number += 1
# Use (question_number - 1) as array index
question = self.question_list[self.question_number - 1]
# Ask user input
user_answer = input(
f"Q.{self.question_number }: {question.text} (True/False): "
)
# Determine the answer
self.check_answer(user_answer, question.answer)
def check_answer(self, user_answer, correct_answer):
if user_answer == correct_answer:
print("Right!")
self.score += 1
else:
print("Opps")
print(f"The correct answer is {correct_answer}")
print(f"The current score is:
{self.score}/{self.question_number}")
With OOP design, QuizBrain did not need to generate the quiz list. The quiz list is passed by caller (main.py). So it is reusable if the quiz resource are coming from different website with different format.
Caller (main.py) just need to format it and pass it when initializing QuizBrain. Then QuizBrain can be reused by different program. That is the beauty of OOP.