Discover challenging Python brain teasers that test your skills and stretch your thinking. Gain insights into advanced concepts and enhance your understanding of this versatile language.

Forget Scrabble, Boggle, or Wordle. Tease your mind and test your skills with these fun brain teasers designed to stretch your thinking and expand your understanding of one of the most widely used languages out there. 

Python is simple. These puzzles are not. Good luck!

Python Brain Teasers

## Try it yourself

Try executing the code below to verify the results:

class timer:
    def __init__(self, name):
        self.name = name

    def __enter__(self):
        ...  

    def __exit__(self, exc_type, exc_value, traceback):
        result = 'OK' if exc_type is None else 'ERROR'
        print(f'{self.name} - {result}')
        return True


with timer('div'):
    1 / 0

## Explanation
Most people expect to see a `ZeroDivisionError` exception in the output of the above code. The `timer` syntax in the code above is a **context manager**. A context manager is used with the `with` statement and is usually for managing resources. For example, the snippet `with open('input.txt')` will make sure that the file is closed after the code inside the context manager is finished, even if the code that contains `with` raises an exception.

There are several types in the Python standard library that can be used with a with statement, including the ones listed below:

- A `file` will be closed.
- A `socket` will be closed.
- A `threading.Lock` will be released.

There’s one resource we don’t need to explicitly manage— the `memory` type. Python has a garbage collector that manages the `memory` for us.

All other resources besides `memory` need to be managed manually. For example, if we forget to close a file, we’ll reach the operating system limit on the number of open files. Our server will start failing after a while if there are too many open files errors.

Some database packages also support `with` statements but use different semantics. If there’s no error, they’ll issue a `COMMIT`. Otherwise, they will issue a `ROLLBACK`.

We can implement context managers by performing either of the following two tasks:

`Write a class with `__enter__` and `__exit__` methods (like we did in the teaser).

Or, use the `contextlib.contextmanager` decorator.

The `__exit__ method` is called when the code that contains the `with` statement is done. Its arguments will be `None` if there was no exception. If `__exit__` returns a `False` value, the exception will propagate. Otherwise, the exception will be suppressed.

Most `__exit__` methods don’t return a value, which, in Python, means it returns `None` with a Boolean value of `False`.

In the teaser, `__exit__` returns `True`, suppressing the `ZeroDivisionError`. 

>**Note:** The `...` in **line 6** is called an ellipsis. It’s valid to use in Python.


# Try it yourself

Try executing the code below to verify the results:

# Explanation
Most people expect to see a `ZeroDivisionError` exception in the output of the above code. The `timer` syntax in the code above is a **context manager**. A context manager is used with the `with` statement and is usually for managing resources. For example, the snippet `with open('input.txt')` will make sure that the file is closed after the code inside the context manager is finished, even if the code that contains `with` raises an exception.

There are several types in the Python standard library that can be used with a with statement, including the ones listed below:

- A `file` will be closed.
- A `socket` will be closed.
- A `threading.Lock` will be released.

There’s one resource we don’t need to explicitly manage— the `memory` type. Python has a garbage collector that manages the `memory` for us.

All other resources besides `memory` need to be managed manually. For example, if we forget to close a file, we’ll reach the operating system limit on the number of open files. Our server will start failing after a while if there are too many open files errors.

Some database packages also support `with` statements but use different semantics. If there’s no error, they’ll issue a `COMMIT`. Otherwise, they will issue a `ROLLBACK`.

We can implement context managers by performing either of the following two tasks:

`Write a class with `__enter__` and `__exit__` methods (like we did in the teaser).

Or, use the `contextlib.contextmanager` decorator.

The `__exit__ method` is called when the code that contains the `with` statement is done. Its arguments will be `None` if there was no exception. If `__exit__` returns a `False` value, the exception will propagate. Otherwise, the exception will be suppressed.

Most `__exit__` methods don’t return a value, which, in Python, means it returns `None` with a Boolean value of `False`.

In the teaser, `__exit__` returns `True`, suppressing the `ZeroDivisionError`. 

>**Note:** The `...` in **line 6** is called an ellipsis. It’s valid to use in Python.


Let’s learn how context managers work when using a with statement.

Before We Begin

Python Puzzles

Wrapping Up

Puzzle 20: Explanation

Try it yourself

Explanation