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

## Let's try it! 
Try executing the code below to verify the result:

class Seeker:
    def __getattribute__(self, name):
        if name not in self.__dict__:  
            return '<not found>'
        return self.__dict__[name]


s = Seeker()
print(s.id)

## Explanation

When we write s.id, Python does an attribute lookup (see Puzzle 1: Ready Player One). Python defines several hooks that bypass the usual attribute lookup algorithm. The two main options are `__getattr__` and `__getattribute__`.

> Note: There are several other ways to modify attribute `access`, including `staticmethod`, `classmethod`, `properties`, `descriptors`, and more.

The `__getattr__` hook method is called when the regular attribute lookup fails. It’s the one we should usually use. Using  `__getattribute__` bypasses the attribute lookup and gives us full control. But, there is the risk of infinite recursion. 

Since `__getattribute__` bypasses the attribute lookup, the code `self.__dict__` in line 3 will call `__getattribute__` again triggering infinite recursion.

Python has a guard against infinite recursions, though. Once the call stack size is more than `sys.getrecursionlimit()` a `RecursionError` will be raised. That’s what we saw happen in the teaser.

Here is the best and least risky way to fix this error. Dictionaries in Python provide a similar hook to the `__getattr__` method called `__missing__`. We can implement `collections.defaultdict` and the like using `__missing__`.

# Let's try it! 
Try executing the code below to verify the result:

# Explanation

When we write s.id, Python does an attribute lookup (see Puzzle 1: Ready Player One). Python defines several hooks that bypass the usual attribute lookup algorithm. The two main options are `__getattr__` and `__getattribute__`.

> Note: There are several other ways to modify attribute `access`, including `staticmethod`, `classmethod`, `properties`, `descriptors`, and more.

The `__getattr__` hook method is called when the regular attribute lookup fails. It’s the one we should usually use. Using  `__getattribute__` bypasses the attribute lookup and gives us full control. But, there is the risk of infinite recursion. 

Since `__getattribute__` bypasses the attribute lookup, the code `self.__dict__` in line 3 will call `__getattribute__` again triggering infinite recursion.

Python has a guard against infinite recursions, though. Once the call stack size is more than `sys.getrecursionlimit()` a `RecursionError` will be raised. That’s what we saw happen in the teaser.

Here is the best and least risky way to fix this error. Dictionaries in Python provide a similar hook to the `__getattr__` method called `__missing__`. We can implement `collections.defaultdict` and the like using `__missing__`.

Let’s learn how to attribute lookup works in Python.

Before We Begin

Python Puzzles

Wrapping Up

Puzzle 12: Explanation

Let’s try it!

Explanation