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πŸ”„ How to define a class variable shared among all instances of a class in Python?

In Python, if you want to define a variable that is shared across all instances of a class, you should define it outside of any method but inside the class β€” this is called a class variable.

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βœ… Correct answer to the question:

> How would you define a class variable that is shared among all instances of a class in Python?

🟒 Option 2: Outside of any method at the class level

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πŸ” Let’s review the other options:

πŸ”΄ Option 1: Inside the constructor method using self
This creates an instance variable, specific to each object, not shared.

πŸ”΄ Option 3: As a local variable inside a method
Local variables are temporary and only exist inside the method scope.

πŸ”΄ Option 4: As a global variable outside the class
Global variables are shared across the entire program, not specific to class instances.

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πŸš— Simple Example: Class Variable in Action

class Car:
wheels = 4 # βœ… class variable, shared across all instances

def __init__(self, brand, color):
self.brand = brand # instance variable
self.color = color # instance variable

car1 = Car("Toyota", "Red")
car2 = Car("BMW", "Blue")

print(Car.wheels) # Output: 4
print(car1.wheels) # Output: 4
print(car2.wheels) # Output: 4

Car.wheels = 6 # changing the class variable

print(car1.wheels) # Output: 6
print(car2.wheels) # Output: 6


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πŸ’‘ Key Takeaways:
- self. creates instance variables β†’ unique to each object.
- Class-level variables (outside methods) are shared across all instances.
- Perfect for shared attributes like constants, counters, or shared settings.



#Python #OOP #ProgrammingTips #PythonLearning #CodeNewbie #LearnToCode #ClassVariables #PythonBasics #CleanCode #CodingCommunity #ObjectOrientedProgramming

πŸ‘¨β€πŸ’» From: https://t.iss.one/DataScienceQ
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πŸ§‘β€πŸŽ“ A Cool Python Tip: How to Access Class Variables? 🐍

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🌟 Scenario:
Imagine you have a variable in a class and want to access it in a method. For example:

class MyClass:
my_variable = "I am a class variable"

def my_method(self):
return f"Accessing variable: {self.my_variable}"

# Test
obj = MyClass()
print(obj.my_method())

πŸ“€ Output: Accessing variable: I am a class variable

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πŸ” Explanation:
- In this example, my_method is a regular instance method with the self argument.
- You can access the class variable with self.my_variable, but you need to create an instance of the class (obj = MyClass()).
- What if you want to access it without creating an instance? That’s where @classmethod comes in! πŸ‘‡

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πŸ’‘ Better Way with @classmethod:
If you want to access the variable directly using the class name, use @classmethod:

class MyClass:
my_variable = "I am a class variable"

@classmethod
def my_method(cls):
return f"Accessing variable: {cls.my_variable}"

# Test
print(MyClass.my_method())

πŸ“€ Output: Accessing variable: I am a class variable

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πŸ”‘ What’s the Difference?
- In the first case (regular method), you need to create an instance to call the method.
- In the second case (with @classmethod), you can call the method directly with the class name (MyClass.my_method()) and cls gives you access to class variables.
- Another option is @staticmethod, but you’d have to manually write the class name (e.g., MyClass.my_variable).

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🎯 Takeaway:
- If you want to work with an instance ➑️ Use a regular method with self.
- If you want to work directly with the class ➑️ Use @classmethod.

Which method do you like more? Drop your thoughts in the comments! πŸ—£οΈ

πŸ’¬ https://t.iss.one/DataScienceQ

#Python #ProgrammingTips #PythonClass
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🧠 Quiz: What is the most "Pythonic" way to create a new list containing the squares of numbers from an existing list called nums?

A) Using a for loop and the .append() method.
B) new_list = [num**2 for num in nums]
C) Using a while loop with an index counter.
D) new_list = (num**2 for num in nums)

βœ… Correct answer: B

Explanation: This is a list comprehension. It's a concise, readable, and often faster way to create a new list from an iterable compared to a traditional for loop. Option D creates a generator expression, not a list.

#Python #ProgrammingTips #PythonQuiz

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By: @DataScienceQ ✨
🧠 Quiz: What is the most Pythonic way to create a new list containing the squares of numbers from 0 to 4?

A) squares = [x**2 for x in range(5)]
B) squares = list(map(lambda x: x**2, range(5)))
C) squares = []
for x in range(5):
squares.append(x**2)

βœ… Correct answer: A

Explanation: List comprehensions are a concise and highly readable way to create lists from other iterables. While the other options work, a list comprehension is generally considered the most "Pythonic" for its clarity and efficiency in this context.

#Python #ProgrammingTips #CodeQuiz

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By: @DataScienceQ ✨
Python tip:

itertools.zip_longest pairs elements from multiple iterables, but unlike the built-in zip(), it continues until the longest iterable is exhausted, padding shorter ones with a specified fillvalue.

While zip() truncates its output to the length of the shortest input, zip_longest() ensures no data is lost from longer inputs by substituting None (or a custom value) for missing items.

ExampleπŸ‘‡
>>> import itertools
>>> students = ['Alice', 'Bob', 'Charlie', 'David']
>>> scores = [88, 92, 75]
>>> grades = list(itertools.zip_longest(students, scores, fillvalue='Absent'))
grades
[('Alice', 88), ('Bob', 92), ('Charlie', 75), ('David', 'Absent')]

#Python #ProgrammingTips #Itertools #PythonTips #CleanCode

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By: @DataScienceQ ✨
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