Python Coding challenge - Day 1137| What is the output of the following Python Code?

 

Code Explanation:

🔹 1. Initializing the List

funcs = []

An empty list funcs is created

This list will store functions

🔹 2. Starting the Loop

for i in range(3):

Loop runs 3 times with values:

i = 0, 1, 2

🔹 3. Defining the Function Inside Loop

def f():

    return i

A function f is defined in each iteration

⚠️ Important: The function does not store the current value of i immediately

Instead, it refers to i (late binding)

👉 This means:

All functions will look up i when they are called, not when they are created

🔹 4. Appending Function to List

funcs.append(f)

The function f is added to the list

After loop ends, funcs contains 3 functions

🔹 5. After Loop Ends

Final value of i is:

i = 2

All functions refer to this same i

🔹 6. Calling the Functions

print([f() for f in funcs])

Each function is called one by one

Each function returns the current value of i, which is 2

🔹 ✅ Final Output

[2, 2, 2]

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Python Coding challenge - Day 1136| What is the output of the following Python Code?

 

Code Explanation:

🔹 1. Metaclass Definition

class Meta(type):

    def __new__(cls, name, bases, dct):

        dct['x'] = 100

        return super().__new__(cls, name, bases, dct)

Meta is a metaclass (inherits from type)

__new__ runs when a class is being created, not an object

It receives the class attributes in dct

It modifies the class dictionary by setting:

x = 100

🔹 2. Class Creation (A)

class A(metaclass=Meta):

    x = 10

Python sends this class definition to the metaclass

Internally:

Meta.__new__(Meta, 'A', (), {'x': 10})

The metaclass changes:

{'x': 10} → {'x': 100}

🔹 3. Final Class Structure

After metaclass processing, class A becomes:

class A:

    x = 100

The original x = 10 is overwritten

🔹 4. Object Creation

obj = A()

Creates an instance of class A

obj itself has no x attribute

🔹 5. Attribute Lookup

print(obj.x)

Python checks:

obj → not found

class A → finds x = 100

🔹 ✅ Final Output

100

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Python Coding challenge - Day 1141| What is the output of the following Python Code?

 

Code Explanation:

🔹 1. Importing Module

import copy

✅ Explanation:

Imports Python’s built-in copy module.

This module provides:

copy.copy() → shallow copy

copy.deepcopy() → deep copy

🔹 2. Creating Nested List

a = [[1,2],[3,4]]

✅ Explanation:

a is a list of lists (nested structure).

Memory structure:

Outer list contains two inner lists

a → [ [1,2], [3,4] ]

🔹 3. Deep Copy

b = copy.deepcopy(a)

✅ Explanation:

Creates a completely independent copy of a.

Both:

Outer list

Inner lists

are copied separately.

🔍 Important:

b ≠ a

b[0] ≠ a[0]

✔️ No shared references

🔹 4. Modifying Copied List

b[0][0] = 100

✅ Explanation:

Changes first element of first inner list in b

So:

b → [ [100,2], [3,4] ]

🔹 5. Printing Original List

print(a)

✅ Explanation:

Since a and b are completely independent,

Changes in b do NOT affect a

🎯 Final Output

[[1, 2], [3, 4]]

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Python Coding challenge - Day 1140| What is the output of the following Python Code?

 

 Code Explanation:

🔹 1. Function Definition

def gen():

✅ Explanation:

A function gen is defined.

Because it uses yield, it becomes a generator function (not a normal function).

🔹 2. First yield

yield 1

✅ Explanation:

yield produces a value without ending the function.

It pauses execution and remembers its state.

🔹 3. Second yield

yield 2

✅ Explanation:

When resumed, the function continues from where it stopped.

Now it yields 2.

🔹 4. Third yield

yield 3

✅ Explanation:

On next resume, it yields 3.

After this, the generator is exhausted.

🔹 5. Creating Generator Object

g = gen()

✅ Explanation:

Calling gen() does NOT execute the function immediately.

It returns a generator object.

Execution starts only when next() is called.

🔹 6. First next() Call

print(next(g))

🔍 What happens:

Starts execution of gen()

Runs until first yield

✔️ Output:

1

🔹 7. Second next() Call

print(next(g))

🔍 What happens:

Resumes from previous pause

Continues to second yield

✔️ Output:

2

🎯 Final Output

1

2

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Python Coding challenge - Day 1139| What is the output of the following Python Code?

 

Code Explanataion:

🧩 1. Decorator Function Definition

def decorator(func):

Defines a function named decorator.

It takes another function (func) as an argument.

This is the core idea of decorators: functions that modify other functions.

🔁 2. Wrapper Function Inside Decorator

    def wrapper():

A nested function wrapper is defined.

This function will replace/extend the behavior of func.

✖️ 3. Modify Original Function Output

        return func() * 2

Calls the original function func().

Multiplies its result by 2.

Returns the modified value.

🔙 4. Return Wrapper Function

    return wrapper

The decorator returns the wrapper function.

This means the original function will be replaced by wrapper.

🎯 5. Applying the Decorator

@decorator

This is syntactic sugar for:

say = decorator(say)

It passes say into decorator and replaces it with wrapper.

📦 6. Original Function Definition

def say():

    return 5

A simple function that returns 5.

But due to the decorator, this function will not run directly.

🔄 7. What Actually Happens Internally

After decoration:

say = decorator(say)

Now say actually refers to wrapper.

When you call say(), it calls wrapper().

🖨️ 8. Function Call and Output

print(say())

Execution Flow:

say() → actually calls wrapper()

wrapper() → calls original func() → returns 5

5 * 2 = 10

✅ Final Output

10

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Python Coding challenge - Day 1138| What is the output of the following Python Code?

 

Code Explanation:

🧩 1. Function Definition: outer

def outer():

This defines a function named outer.

It acts as an enclosing (parent) function.

📦 2. Variable Initialization

    x = 10

A local variable x is created inside outer.

Initial value of x is 10.

🔁 3. Inner Function Definition

    def inner():

A nested function named inner is defined inside outer.

It has access to variables of outer (like x).

🔗 4. Using nonlocal

        nonlocal x

nonlocal means:

“Use the variable x from the nearest enclosing scope (outer function), not create a new one.”

Without nonlocal, modifying x would cause an error.

➕ 5. Modify the Variable

        x += 5

Adds 5 to the existing value of x.

Since x is nonlocal, it updates the outer function’s x.

🔙 6. Return Updated Value

        return x

Returns the updated value of x.

📤 7. Return Inner Function

    return inner

The outer function returns the inner function itself, not its result.

This creates a closure (function + its environment).

🎯 8. Create Function Instance

f = outer()

Calls outer(), which returns inner.

Now f becomes a reference to inner, with x = 10 preserved.

🖨️ 9. Function Calls and Output

print(f(), f())

First Call: f()

x = 10

x += 5 → 15

Returns 15

Second Call: f()

x = 15 (value persists due to closure)

x += 5 → 20

Returns 20

✅ Final Output

15 20

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Python Coding challenge - Day 1131| What is the output of the following Python Code?

 

Code Explanation:

🔹 1. Base Class Definition

class A: 

    pass

✅ Explanation:

A class A is created.

pass means the class has no attributes or methods (empty class).

🔹 2. Derived Class (Inheritance)

class B(A): 

    pass

✅ Explanation:

Class B is created and inherits from class A.

This means:

B gets all properties of A.

B IS-A A (important concept in OOP).

🔹 3. Object Creation

obj = B()

✅ Explanation:

An object obj of class B is created.

So:

obj belongs to class B

But also indirectly belongs to class A (because of inheritance)

🔹 4. isinstance() Check

isinstance(obj, A)

✅ Explanation:

Checks if obj is:

An instance of class A OR

Any subclass of A

🔍 In this case:

obj is instance of B

B inherits from A

So:

True

🔹 5. type() Comparison

type(obj) == A

✅ Explanation:

type(obj) returns the exact class of the object.

Here:

type(obj) → B

So comparison becomes:

B == A  → False

🔹 6. Final Print Statement

print(isinstance(obj, A), type(obj) == A)

✅ Output:

True False

🎯 Final Output

True False

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Python Coding challenge - Day 1130| What is the output of the following Python Code?

 

Code Explanation:

🔹 1. Class Definition

class Test:

✅ Explanation:

A class named Test is created.

It will contain a variable and two methods.

🔹 2. Class Variable

x = 10

✅ Explanation:

x is a class variable.

Shared across all instances of the class.

Accessible via:

Test.x

cls.x (inside class methods)

🔹 3. Class Method (@classmethod)

@classmethod

def show(cls):

    return cls.x

✅ Explanation:

@classmethod decorator defines a method that works with the class, not instance.

cls refers to the class (Test).

🔍 What happens:

cls.x → accesses class variable x

Returns:

10

🔹 4. Static Method (@staticmethod)

@staticmethod

def display():

    return Test.x

✅ Explanation:

@staticmethod creates a method that:

Does NOT take self or cls

Works like a normal function inside the class

🔍 What happens:

Directly accesses:

Test.x

Returns:

10

🔹 5. Calling Methods

print(Test.show(), Test.display())

✅ Step-by-step:

➤ Test.show()

Calls class method

cls = Test

Returns:

10

➤ Test.display()

Calls static method

Returns:

10

🎯 Final Output

10 10

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Python Coding challenge - Day 1129| What is the output of the following Python Code?

 

Code Explanation:

🔹 1. Class Definition

class Test:

✅ Explanation:

A class named Test is created.

This class will define how its objects are represented as strings.

🔹 2. __str__ Method

def __str__(self):

    return "STR"

✅ Explanation:

__str__ is a magic method used for user-friendly string representation.

It is called when:

print(obj)

str(obj)

Here, it returns:

"STR"

🔹 3. __repr__ Method

def __repr__(self):

    return "REPR"

✅ Explanation:

__repr__ is another magic method used for:

Debugging

Developer-friendly representation

It is called when:

You type obj in interpreter

Or when __str__ is not defined

🔹 4. Creating Object

obj = Test()

✅ Explanation:

An object obj of class Test is created.

No constructor (__init__) is defined, so default is used.

🔹 5. Printing Object

print(obj)

✅ What happens internally:

Python follows this priority:

Call __str__()

If not available → call __repr__()

🔍 In this case:

__str__ exists → used

So:

obj.__str__()

returns:

"STR"

🎯 Final Output

STR

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Python Coding challenge - Day 1127| What is the output of the following Python Code?

 

Code Explanation:

🔹 1. Class Definition

class Test:

    x = []

✅ Explanation:

A class named Test is created.

x = [] is a class variable (shared by all objects).

This means:

Only one list exists in memory.

All instances (a, b, etc.) will refer to the same list unless overridden.

🔹 2. Constructor (__init__ method)

def __init__(self, value):

    self.x.append(value)

✅ Explanation:

This method runs whenever an object is created.

self refers to the current object.

self.x.append(value):

Python first looks for x inside the instance.

Not found → it looks in the class.

Finds x (the shared list).

So, it appends the value to the same shared list.

🔹 3. Creating First Object

a = Test(1)

✅ What happens:

Object a is created.

__init__(1) runs.

self.x.append(1) → list becomes:

[1]

🔹 4. Creating Second Object

b = Test(2)

✅ What happens:

Object b is created.

__init__(2) runs.

Again, self.x refers to the same class list.

2 is appended → list becomes:

[1, 2]

🔹 5. Printing Values

print(a.x, b.x)

✅ Explanation:

Both a.x and b.x refer to the same list.

So output is:

[1, 2] [1, 2]

⚠️ Key Concept (Very Important)

🔸 Class Variable vs Instance Variable

Type Defined Where Shared?

Class Variable Inside class ✅ Yes

Instance Variable Inside __init__ using self ❌ No

🔥 Why This Happens

Because:

x = []

is defined at class level, not inside __init__.

✅ How to Fix (If You Want Separate Lists)

class Test:

    def __init__(self, value):

        self.x = []      # instance variable

        self.x.append(value)

✔️ Output now:

[1] [2]

🎯 Final Answer

[1, 2] [1, 2]

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Python Coding challenge - Day 1126| What is the output of the following Python Code?

 

Code Explanation:

1️⃣ Defining the Class

class A:

Explanation

A class A is created.

It will contain variables and methods.

2️⃣ Defining Class Variable

x = 10

Explanation

x is a class variable.

It belongs to the class, not individual objects.

3️⃣ Defining @classmethod

@classmethod

def f(cls):

Explanation

f is a class method.

It receives the class itself as cls.

4️⃣ Accessing Class Variable via cls

return cls.x

Explanation

Accesses class variable x using cls.

Works for inheritance too (dynamic reference).

5️⃣ Defining @staticmethod

@staticmethod

def g():

Explanation

g is a static method.

It does NOT receive self or cls.

6️⃣ Accessing Class Variable Directly

return A.x

Explanation

Directly accesses class A.

Not flexible for inheritance (hardcoded).

7️⃣ Calling Methods

print(A.f(), A.g())

Explanation

Calls both methods using class A.

🔄 Method Execution

🔹 A.f()

cls = A

Returns:

A.x → 10

🔹 A.g()

Directly returns:

A.x → 10

📤 Final Output

10 10

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Python Coding challenge - Day 1125| What is the output of the following Python Code?

 

Code Explanation:

1️⃣ Importing dataclass

from dataclasses import dataclass

Explanation

Imports the dataclass decorator.

It auto-generates methods like __init__, __repr__, etc.

2️⃣ Applying @dataclass

@dataclass

Explanation

Converts class A into a dataclass.

Automatically creates constructor like:

def __init__(self, x=[]):

    self.x = x

⚠️ Important: x=[] is evaluated once, not per object.

3️⃣ Defining Class

class A:

Explanation

Defines class A.

4️⃣ Defining Attribute with Default Value

x: list = []

Explanation ⚠️ CRITICAL

x is given a default value of an empty list.

This list is shared across all instances.

👉 Only ONE list is created in memory.

5️⃣ Creating First Object

a1 = A()

Explanation

a1.x refers to the shared list.

6️⃣ Creating Second Object

a2 = A()

Explanation

a2.x refers to the same shared list.

👉 So:

a1.x is a2.x → True

7️⃣ Modifying List from a1

a1.x.append(1)

Explanation

Adds 1 to the shared list.

👉 Now shared list becomes:

[1]

8️⃣ Printing from a2

print(a2.x)

Explanation

Since a2.x points to the same list:

[1]

📤 Final Output

[1]

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Python Coding challenge - Day 1124| What is the output of the following Python Code?

 

Code Explanation:

1️⃣ Importing Enum

from enum import Enum

Explanation

Imports the Enum class from Python’s enum module.

Used to create enumerations (named constants).

2️⃣ Defining Enum Class

class Color(Enum):

Explanation

Creates an enum class named Color.

It inherits from Enum.

3️⃣ Defining Enum Members

RED = 1

BLUE = 2

Explanation

Defines two enum members:

Color.RED → value 1

Color.BLUE → value 2

👉 These are unique objects, not just numbers.

4️⃣ Comparing Enum Values

print(Color.RED == Color(1))

Explanation

Color.RED → enum member

Color(1) → converts value 1 into enum member

👉 So:

Color(1) → Color.RED

5️⃣ Final Comparison

Color.RED == Color.RED

Explanation

Both refer to the same enum member.

📤 Final Output

True

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Python Coding challenge - Day 1123| What is the output of the following Python Code?

 

Code Explanation:

1️⃣ Importing lru_cache

from functools import lru_cache

Explanation

Imports lru_cache from the functools module.

It is used for memoization (caching function results).

2️⃣ Applying Decorator

@lru_cache(None)

Explanation

This decorator caches results of function calls.

None means unlimited cache size.

👉 So once a value is computed, it is stored and reused.

3️⃣ Defining Function

def f(n):

Explanation

Defines function f that takes input n.

4️⃣ Base Condition

if n <= 1:

    return n

Explanation

If n is 0 or 1, return n.

This is the base case of recursion.

5️⃣ Recursive Case

return f(n-1) + f(n-2)

Explanation

This is Fibonacci logic.

Computes:

f(n) = f(n-1) + f(n-2)

6️⃣ Calling Function

print(f(5))

Explanation

Calls f(5).

🔄 Execution (Step-by-Step)

Without cache:

f(5)

= f(4) + f(3)

= (f(3)+f(2)) + (f(2)+f(1))

= ...

👉 Many repeated calls!

⚡ With lru_cache

Each value is computed once only:

Call Value

f(0) 0

f(1) 1

f(2) 1

f(3) 2

f(4) 3

f(5) 5

📤 Final Output

5

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Python Coding challenge - Day 1122| What is the output of the following Python Code?

 

Code Explanation:

📌 1. Class A Definition

class A:

    def show(self, x=1):

        return x

✅ What happens:

A class A is created.

Method show():

Takes parameter x

Default value → 1

Returns x as it is

📌 2. Class B Definition (Inheritance)

class B(A):

✅ What happens:

B inherits from A

So B gets access to:

All methods of A

Including show()

📌 3. Method Overriding in B

def show(self, x=2):

    return super().show(x+1)

✅ Key Concepts:

🔹 1. Method Overriding

B defines its own show()

This overrides A.show()

🔹 2. Default Argument Change

In A: x = 1

In B: x = 2

👉 So calling obj.show() will use:

x = 2

🔹 3. Use of super()

super().show(x+1)

Calls parent class (A) method

Passes modified value: x + 1

📌 4. Object Creation

obj = B()

✅ What happens:

Object obj of class B is created

It will use B's methods first (due to method overriding)

📌 5. Function Call

print(obj.show())

📌 6. Step-by-Step Execution

🔹 Step 1: Call obj.show()

Since B overrides → B.show() is called

Default value:

x = 2

🔹 Step 2: Inside B.show()

return super().show(x+1)

👉 Compute:

x + 1 = 2 + 1 = 3

🔹 Step 3: Call Parent Method

A.show(3)

🔹 Step 4: Inside A.show()

return x

👉 Returns:

3

📌 7. Final Output

3

✅ Final Answer

3

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Python Coding challenge - Day 1121| What is the output of the following Python Code?

 

Code Explanation:

1. Class Definition Phase

class Test:

    x = 10

✅ What happens:

A class named Test is created.

A class variable x is defined and assigned value 10.

👉 At this point:

Test.x = 10

📌 2. Constructor (__init__) Definition

def __init__(self):

    self.x = self.x + 5

✅ What happens:

This runs every time an object is created.

self.x refers to:

First tries instance variable

If not found → falls back to class variable

📌 3. Creating First Object (t1)

t1 = Test()

Step-by-step:

🔹 Step 1: Object is created

Python creates a new object t1.

🔹 Step 2: __init__ runs

self.x = self.x + 5

self.x → no instance variable yet

So Python looks at class variable → Test.x = 10

👉 Calculation:

self.x = 10 + 5 = 15

🔹 Step 3: Instance variable created

Now:

t1.x = 15   (instance variable)

📌 4. Creating Second Object (t2)

t2 = Test()

Step-by-step:

Same process repeats:

self.x → still no instance variable

Uses class variable again → 10

👉 Calculation:

self.x = 10 + 5 = 15

Now:

t2.x = 15

📌 5. Important Concept: Class vs Instance Variable

At this point:

Variable Value

Test.x 10

t1.x 15

t2.x 15

👉 Key idea:

self.x = ... creates a new instance variable

It does NOT modify the class variable

📌 6. Final Print Statement

print(t1.x, t2.x, Test.x)

Values:

t1.x → 15

t2.x → 15

Test.x → 10

✅ Final Output

15 15 10

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Python Coding challenge - Day 1120| What is the output of the following Python Code?

 

Code Explanation:

1️⃣ Importing Threading Module

import threading

Explanation

Imports Python’s threading module.

Used to create and run threads.

2️⃣ Defining Task Function

def task():

    print("X")

Explanation

Defines a function task.

This function prints "X".

It will be executed by threads.

3️⃣ Creating First Thread

t1 = threading.Thread(target=task)

Explanation

Creates thread t1.

It will run the task() function.

4️⃣ Creating Second Thread

t2 = threading.Thread(target=task)

Explanation

Creates another thread t2.

Also runs task().

5️⃣ Starting First Thread

t1.start()

Explanation

Starts execution of thread t1.

It runs:

task() → print("X")

6️⃣ Starting Second Thread

t2.start()

Explanation

Starts execution of thread t2.

It also runs:

task() → print("X")

7️⃣ Printing from Main Thread

print("Main")

Explanation

This runs in the main thread.

It does NOT wait for t1 or t2 (no join() used).

⚠️ Important Behavior (Execution Order)

Threads run concurrently.

There is no guarantee of order.

Possible outputs:

📤 Possible Outputs

Case 1

X

X

Main

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Python Coding challenge - Day 1119| What is the output of the following Python Code?

 

Code Explanation:

1️⃣ Importing Threading Module

import threading

Explanation

Imports Python’s threading module.

Used for creating threads and locks.

2️⃣ Creating an RLock

lock = threading.RLock()

Explanation

Creates a Reentrant Lock (RLock).

Special lock that allows same thread to acquire it multiple times.

👉 Unlike normal Lock, this avoids deadlock when re-acquired.

3️⃣ Defining Task Function

def task():

Explanation

Function that will run inside the thread.

4️⃣ First Lock Acquisition

with lock:

Explanation

Thread acquires the lock.

Ensures only one thread enters this block at a time.

5️⃣ Printing First Value

print("A")

Explanation

Prints:

A

6️⃣ Nested Lock Acquisition

with lock:

Explanation ⚠️ IMPORTANT

Same thread tries to acquire the lock again.

Since it's an RLock, this is allowed.

👉 With normal Lock, this would cause deadlock ❌

7️⃣ Printing Second Value

print("B")

Explanation

Prints:

B

8️⃣ Creating Thread

t = threading.Thread(target=task)

Explanation

Creates a thread that will execute task().

9️⃣ Starting Thread

t.start()

Explanation

Thread starts execution.

Runs task().

🔟 Waiting for Completion

t.join()

Explanation

Main thread waits until task() finishes.

📤 Final Output

A

B

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Python Coding challenge - Day 1118| What is the output of the following Python Code?

 

Code Explanation:

1️⃣ Importing dataclass

from dataclasses import dataclass

Explanation

Imports the dataclass decorator.

It helps automatically generate methods like:

__init__

__repr__

__eq__

2️⃣ Applying @dataclass Decorator

@dataclass

Explanation

This decorator modifies class A.

Automatically adds useful methods.

Saves you from writing boilerplate code.

3️⃣ Defining the Class

class A:

Explanation

A class A is created.

It will hold data (like a structure).

4️⃣ Defining Attributes with Type Hints

x: int

y: int

Explanation

Defines two attributes:

x of type int

y of type int

These are used by @dataclass to generate constructor.

5️⃣ Auto-Generated Constructor

👉 Internally, Python creates:

def __init__(self, x, y):

    self.x = x

    self.y = y

Explanation

You don’t write this manually.

@dataclass creates it automatically.

6️⃣ Creating Object

a = A(1,2)

Explanation

Calls auto-generated __init__.

Assigns:

a.x = 1

a.y = 2

7️⃣ Printing Object

print(a)

Explanation

Calls auto-generated __repr__() method.

👉 Internally behaves like:

"A(x=1, y=2)"

📤 Final Output

A(x=1, y=2)

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Python Coding challenge - Day 1117| What is the output of the following Python Code?

 

Code Explanation:

1️⃣ Importing chain

from itertools import chain

Explanation

Imports chain from Python’s itertools module.

chain is used to combine multiple iterables.

2️⃣ Creating First List

a = [1,2]

Explanation

A list a is created with values:

[1, 2]

3️⃣ Creating Second List

b = [3,4]

Explanation

Another list b is created:

[3, 4]

4️⃣ Using chain()

chain(a, b)

Explanation

chain(a, b) links both lists sequentially.

It does NOT create a new list immediately.

It returns an iterator.

👉 Internally behaves like:

1 → 2 → 3 → 4

5️⃣ Converting to List

list(chain(a, b))

Explanation

Converts the iterator into a list.

Collects all elements in order.

6️⃣ Printing Result

print(list(chain(a, b)))

Explanation

Displays the combined list.

📤 Final Output

[1, 2, 3, 4]

Book:  700 Days Python Coding Challenges with Explanation

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