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 result:

def add(a: int, b: int) -> int: 
  return a + b

val = add('1', '2') 
print(val)

# Explanation

Python 3 added support for **type hints**. As the name suggests, though,  they’re only hints that are not enforced by the Python interpreter. The only thing Python does with these hints (sometimes called annotations) is to add them to the function object as the `annotations` attribute.
``` Python
>>> add.__annotations__
{'a': int, 'b': int, 'return': int}
```
Over time, type annotation becomes more powerful. We can annotate variables (like `answer: int = 42`) and attributes. There’s a dedicated typing module and more.

You might wonder why type annotation is so popular. Here are some reasons listed below:

- **Correctness** gets ensured through external tools like  Mypy that will check type correctness. Some teams have Mypy as part of their test suite.
- **Documentation** is easy with type annotation. When we see a definition like `def current_user(session: dict) → User:`, we know what the input and output types are.
- **Tools** can learn the type of object and become smarter. Most IDEs (such as `PyCharm`) use type annotation to help with completion.
- **Code** is easier to write with type annotation. Once we have annotations, we can write modules like `dataclasses`.

Now back to our teaser. We add `a` and `b`, which are of type `str`. The `+` operator (defined by `add`) in `str` does concatenation. For example, it makes `‘a’ + ‘b’` → `‘ab’`.


Let’s learn about type annotations in Python.

Before We Begin

Python Puzzles

Wrapping Up

Puzzle 29: Explanation