Python Coding challenge - Day 1189| What is the output of the following Python Code?

 

Code Explanation:

🔹 1. Creating a List

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

✅ Explanation:

A list named nums is created.

Contents:

[1, 2, 3, 4, 5]

Current state:

nums

 ↓

[1, 2, 3, 4, 5]

🔹 2. Calling filter()

filter(lambda x: x % 2 == 0, nums)

✅ Explanation:

The filter() function checks every element of the list and keeps only those elements for which the condition returns True.

Syntax:

filter(function, iterable)

Here:

lambda x: x % 2 == 0

means:

Keep only even numbers.

🔹 3. Understanding the Lambda Function

lambda x: x % 2 == 0

✅ Explanation:

This lambda function checks whether a number is divisible by 2.

Equivalent code:

def check(x):

    return x % 2 == 0

Examples:

1 % 2 = 1 → False ❌

2 % 2 = 0 → True ✅

3 % 2 = 1 → False ❌

4 % 2 = 0 → True ✅

5 % 2 = 1 → False ❌

🔹 4. Result of filter()

Python checks every element one by one.

Number Condition Action

1 False Remove ❌

2 True Keep ✅

3 False Remove ❌

4 True Keep ✅

5 False Remove ❌

After filtering:

2

4

The filter object contains:

2, 4

🔹 5. Calling map()

map(

    lambda x: x * 10,

    filter(...)

)

✅ Explanation:

Now map() receives the filtered values:

2

4

Its job is to apply a function to every element.

Syntax:

map(function, iterable)

🔹 6. Understanding the Second Lambda

lambda x: x * 10

✅ Explanation:

This lambda multiplies every value by 10.

Equivalent function:

def multiply(x):

    return x * 10

🔹 7. First Iteration of map()

Current value:

x = 2

Calculation:

2 * 10

Result:

20

🔹 8. Second Iteration of map()

Current value:

x = 4

Calculation:

4 * 10

Result:

40

🔹 9. Result of map()

Generated values:

20

40

Internally:

map object

Not a list yet.

🔹 10. Converting to List

list(result)

✅ Explanation:

The map object is converted into a normal list.

Result:

[20, 40]

🔹 11. Printing the Output

print(list(result))

✅ Explanation:

Prints:

[20, 40]

🎯 Final Output

[20, 40]

Book:  700 Days Python Coding Challenges with Explanation