🚀 Day 59/150 – Rotate a List in Python

Rotating a list means shifting its elements either to the left or to the right.

Example:
[1, 2, 3, 4, 5]

Rotate right by 2 → [4, 5, 1, 2, 3]
Rotate left by 2 → [3, 4, 5, 1, 2]

Let’s explore different ways to rotate a list 👇

🔹 Method 1 – Right Rotation Using Slicing

numbers = [1, 2, 3, 4, 5] k = 2 rotated = numbers[-k:] + numbers[:-k] print("Right Rotated:", rotated)

🔹 Method 2 – Left Rotation Using Slicing

numbers = [1, 2, 3, 4, 5] k = 2 rotated = numbers[k:] + numbers[:k] print("Left Rotated:", rotated)

🔹 Method 3 – Using Loop (Right Rotation by One)

numbers = [1, 2, 3, 4, 5] last = numbers[-1] for i in range(len(numbers) - 1, 0, -1): numbers[i] = numbers[i - 1] numbers[0] = last print("Rotated List:", numbers)

🔹 Method 4 – Taking User Input

numbers = list(map(int, input("Enter numbers: ").split())) k = int(input("Enter rotation count: ")) k = k % len(numbers) rotated = numbers[-k:] + numbers[:-k] print("Rotated List:", rotated)

💡 Key Takeaways

• Slicing is the easiest way to rotate a list
• Use k % len(list) to handle large rotation values
• Right rotation uses [-k:] +[:-k]
• Left rotation uses [k:] +[:k]

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Python Coding Challenge - Question with Answer (ID -050626)

 

Explanation:

🔹 Step 1: Create Empty List

x = []

An empty list is created:

[]

Memory:

x ──► []

🔹 Step 2: Append the List to Itself

x.append(x)

Normally we do:

x.append(1)

or

x.append("A")

But here we're doing:

x.append(x)

which means:

Append the list itself inside itself

After execution:

x = [x]

Visual representation:

x

│

▼

[ x ]

More accurately:

x

│

▼

The list contains a reference to itself.

🔹 Step 3: Understand x[0]

x[0]

First element of the list is:

x

itself.

So:

x[0] is x

becomes:

True

Both point to the exact same object.

🔹 Step 4: Evaluate Comparison

x == x[0]

Substitute:

x == x

Python is effectively comparing the same object with itself.

Result:

True

🔹 Step 5: Print Result

print(True)

Output:

True

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🚀 Day 58/150 – Find Unique Elements in a List in Python

 

🚀 Day 58/150 – Find Unique Elements in a List in Python

Unique elements are values that appear only once in the list.

Example:
[1, 2, 2, 3, 4, 4, 5] → Unique elements = [1, 3, 5]

Let’s explore different ways to find them 👇

🔹 Method 1 – Using Loop

numbers = [1, 2, 2, 3, 4, 4, 5] unique = [] for num in numbers: if numbers.count(num) == 1: unique.append(num) print("Unique Elements:", unique)

🔹 Method 2 – Using List Comprehension

numbers = [1, 2, 2, 3, 4, 4, 5] unique = [num for num in numbers if numbers.count(num) == 1] print("Unique Elements:", unique)

🔹 Method 3 – Using collections.Counter

from collections import Counter numbers = [1, 2, 2, 3, 4, 4, 5] freq = Counter(numbers) unique = [num for num in numbers if freq[num] == 1] print("Unique Elements:", unique)

🔹 Method 4 – Taking User Input

numbers = list(map(int, input("Enter numbers: ").split())) unique = [num for num in numbers if numbers.count(num) == 1] print("Unique Elements:", unique)

💡 Key Takeaways

• Unique elements appear exactly once
• count() is easy to understand but slower for large lists
• Counter is better for larger datasets
• Useful in data cleaning and duplicate detection

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Python Coding challenge - Day 1161| What is the output of the following Python Code?

 

Code Explanation:

🔹 1. Creating the List

nums = [1, 2, 3, 4, 5]

✅ Explanation:

A list named nums is created.

It contains:

[1, 2, 3, 4, 5]

🔹 2. Using filter()

result = filter(

✅ Explanation:

filter() is a built-in Python function.

It filters elements based on a condition.

Syntax:

filter(function, iterable)

function → returns True or False

iterable → list, tuple, etc.

🔹 3. Lambda Function

lambda x: x % 2 == 0

✅ Explanation:

This is an anonymous function.

Equivalent code:

def check(x):

    return x % 2 == 0

Condition:

x % 2 == 0

Checks whether a number is even.

🔹 4. Passing the List

nums

✅ Explanation:

The lambda function will be applied to each element of:

[1, 2, 3, 4, 5]

🔹 5. Internal Working of filter()

Python checks every element one by one.

🔍 For 1

1 % 2 == 0

Result:

False

❌ Rejected

🔍 For 2

2 % 2 == 0

Result:

True

✅ Kept

🔍 For 3

3 % 2 == 0

Result:

False

❌ Rejected

🔍 For 4

4 % 2 == 0

Result:

True

✅ Kept

🔍 For 5

5 % 2 == 0

Result:

False

❌ Rejected

🔹 6. Result After Filtering

Remaining values:

2

4

So internally:

filter object → [2, 4]

🔹 7. Converting to List

print(list(result))

✅ Explanation:

filter() returns a filter object (iterator).

list() converts it into a list.

Result:

[2, 4]

🎯 Final Output

[2, 4]

300 Days Python Coding Challenges with Explanation

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Python Coding challenge - Day 1160| What is the output of the following Python Code?

 

Code Explanation:

🔹 1. Creating an Empty List

context = []

✅ Explanation:

An empty list named context is created.

Current state:

[]

🔹 2. Starting the Loop

for i in range(3):

✅ Explanation:

range(3) generates:

0, 1, 2

Loop will run 3 times.

🔹 3. First Iteration

Value of i

i = 0

Executing

context.append(i)

List becomes

[0]

🔹 4. Second Iteration

Value of i

i = 1

Executing

context.append(i)

List becomes

[0, 1]

🔹 5. Third Iteration

Value of i

i = 2

Executing

context.append(i)

List becomes

[0, 1, 2]

🔹 6. Loop Ends

After all iterations:

context

contains:

[0, 1, 2]

🔹 7. Removing First Element

context.pop(0)

✅ Explanation:

pop(index) removes and returns the element at that index.

Here index is:

0

which is the first element.

Removed value:

0

List becomes:

[1, 2]

🔹 8. Printing the List

print(context)

✅ Explanation:

Prints the final contents of the list.

🎯 Final Output

[1, 2]

BOOK: 100 Python Programs for Beginner with explanation

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Python Coding Challenge - Question with Answer (ID -040626)

 

Explanation:

🔹 Step 1: Import partial

from functools import partial

partial() is a utility from the functools module.

It allows you to:

Fix some arguments of a function

in advance.

Think of it as creating a new function with some arguments already filled in.

🔹 Step 2: Create Partial Function

f = partial(pow, 2)

Original function:

pow(a, b)

Meaning:

a ** b

Examples:

pow(2,3) → 8

pow(3,2) → 9

Now:

partial(pow, 2)

fixes the first argument as:

2

So Python creates a new function equivalent to:

def f(b):

    return pow(2, b)

🔹 Step 3: Execute f(5)

f(5)

Internally becomes:

pow(2, 5)

Because:

2

was already fixed by partial().

🔹 Step 4: Calculate Power

pow(2, 5)

means:

2 × 2 × 2 × 2 × 2

Result:

32

🔹 Step 5: Print Result

print(32)

Output:

32

Book: 1000 Days Python Coding Challenges with Explanation

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🚀 Day 57/150 – Find Common Elements in Lists in Python

 

🚀 Day 57/150 – Find Common Elements in Lists in Python

Finding common elements means identifying values that appear in both lists.

This is useful in filtering, comparisons, and matching datasets.

🔹 Method 1 – Using Loop

list1 = [1, 2, 3, 4, 5] list2 = [3, 4, 5, 6, 7] common = [] for num in list1: if num in list2: common.append(num) print("Common Elements:", common)

🔹 Method 2 – Using List Comprehension

list1 = [1, 2, 3, 4, 5] list2 = [3, 4, 5, 6, 7] common = [num for num in list1 if num in list2] print("Common Elements:", common)

🔹 Method 3 – Using set()

list1 = [1, 2, 3, 4, 5]
list2 = [3, 4, 5, 6, 7]

common = list(set(list1) & set(list2))

print("Common Elements:", common)

🔹 Method 4 – Taking User Input

list1 = list(map(int, input("Enter first list: ").split()))



list2 = list(map(int, input("Enter second list: ").split()))

common = [num for num in list1 if num in list2]

print("Common Elements:", common)

💡 Key Takeaways

• Loop method is easiest to understand
• List comprehension gives a shorter solution
• set() is faster for large lists
• Useful in comparisons, filtering, and duplicate checking

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