Python Coding Challenge - Question with Answer (ID -060726)

 

Explanation:

Creating an Iterator

Code

x = iter(lambda: 2, 2)

Explanation

iter() is a built-in Python function.

Here, it uses the syntax:

iter(callable, sentinel)

It repeatedly calls a function (callable) until it returns the sentinel value.

The created iterator is stored in the variable x.

 Understanding lambda: 2

Code

lambda: 2

Explanation

lambda creates an anonymous function.

It takes no arguments.

Every time it is called, it returns 2.

Equivalent code:

def func():

    return 2

Understanding the Sentinel Value

Code

2

Explanation

The second argument of iter() is called the sentinel.

It tells the iterator when to stop.

Rule:

If the function returns 2, stop the iteration.

How the Iterator Works

Python internally performs these steps:

value = lambda()

if value == 2:

    stop iteration

else:

    yield value

First Function Call

lambda() → 2

Comparison:

2 == 2

Result:

True

Therefore, the iterator stops immediately.

Converting the Iterator to a List

print(list(x))

Explanation

list(x) reads all values from the iterator.

Since the iterator has already stopped, there are no values.

Therefore, it returns an empty list.

[]

Output

[]

Book: Mastering Pandas with Python