Hackerrank File I/O and Exception Handling 5

Question 1

What is the correct way to raise a custom exception with a message in Python?

Accepted Answer

raise Exception('msg')

Answer

In Python, you use `raise ExceptionClass(args)` to raise an exception with a message.

Question 2

Given `with open('data.txt', 'w') as f: f.write('hello')`, what is the state of the file after the `with` block exits normally?

Accepted Answer

The file is closed and contains 'hello'

Answer

Exiting a `with` block calls `__exit__`, which flushes the write buffer and closes the file, so 'hello' is persisted.

Question 3

Which exception class should a custom exception inherit from to be considered a user-defined application error?

Accepted Answer

Exception

Answer

Custom exceptions should inherit from `Exception` (not `BaseException`) so they don't accidentally catch system-exit signals.

Question 4

What does the `truncate(size)` method do when called on a writable file object?

Accepted Answer

Resizes the file to at most `size` bytes

Answer

`truncate(size)` resizes the file so it is at most `size` bytes, padding with null bytes if size is larger than the current file.

Question 5

What will the following code print?
```python
try:
    raise ValueError('oops')
except TypeError:
    print('type')
except ValueError:
    print('value')
```

Accepted Answer

value

Answer

The `ValueError` exception matches the second `except` clause, so 'value' is printed.

(Hackerrank) HackerRank Python Certification Practice Test

(Hackerrank) HackerRank Python Certification Practice Test

Hackerrank File I/O and Exception Handling 5