Hackerrank - HackerRank Python Control Flow and Looping Questions and Answers

Question 1

What is the output of the following Python code snippet?

```python
for i in range(5):
    if i == 3:
        continue
    print(i, end=' ')
else:
    print('Loop finished', end='')
```

Accepted Answer

0 1 2 4 Loop finished

Answer

The `for` loop iterates from 0 to 4. The `continue` statement is triggered when `i` is 3, which skips the `print(i)` statement for that iteration and proceeds to the next one. The `else` block of a `for` loop executes only when the loop completes its iterations without being terminated by a `break` statement. Since no `break` occurs, 'Loop finished' is printed after the loop concludes.

Question 2

A developer is writing a function but has not yet implemented its logic. To avoid an `IndentationError` for an empty code block, which keyword should be used as a placeholder?

Accepted Answer

pass

Answer

The `pass` statement in Python is a null operation. It is used when a statement is required syntactically but you do not want any command or code to execute. It's a common placeholder for function bodies or conditional blocks that are yet to be implemented.

Question 3

What will the following Python code print to the console?

```python
count = 5
while count > 1:
    print(count)
    count -= 1
    if count == 3:
        break
else:
    print('Done')
```

Accepted Answer

5
4

Answer

The `while` loop starts with `count` as 5. It prints 5 and then 4. When `count` becomes 3, the `if` condition is met, and the `break` statement is executed. The `break` statement immediately terminates the loop. The `else` block associated with a loop is only executed if the loop finishes normally (i.e., its condition becomes false), not when it is terminated by a `break` statement.

Question 4

Which of the following scenarios is the most appropriate use case for a `for` loop with an `else` block in Python?

Accepted Answer

Searching for an item in a list and performing an action only if the item is not found.

Answer

The `else` block of a `for` loop is executed if and only if the loop completes its entire sequence of iterations without encountering a `break` statement. This makes it ideal for search operations. You can use the `for` loop to look for an item, `break` if it's found, and the `else` block will then only run if the entire list was searched and the item was not found.

Question 5

Analyze the following nested loop. How many times will the `print('*')` statement be executed?

```python
for i in range(3):
    for j in range(i + 1):
        print('*')
```

Accepted Answer

6

Answer

The outer loop iterates with `i` taking values 0, 1, and 2. 
- When `i` is 0, the inner loop `range(1)` runs once (j=0).
- When `i` is 1, the inner loop `range(2)` runs twice (j=0, 1).
- When `i` is 2, the inner loop `range(3)` runs three times (j=0, 1, 2).
The total number of executions for `print('*')` is 1 + 2 + 3 = 6.

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Hackerrank - HackerRank Python Control Flow and Looping Questions and Answers