How to type hint functions in python

python type hinting: a comprehensive guide

type hinting in python, introduced in pep 484 (python 3.5) and further refined in subsequent peps, is a powerful feature that allows you to specify the expected data types of function arguments and return values. while python remains a dynamically-typed language, type hints offer significant benefits, including improved code readability, better static analysis (catching errors early), and enhanced maintainability.

this tutorial will guide you through the intricacies of type hinting, covering everything from basic types to more advanced concepts like generics, `union` types, and custom type aliases. we'll illustrate each concept with practical code examples.

**why use type hints?**

before diving into the "how," let's reiterate the "why":

* **readability:** type hints make your code easier to understand at a glance. you instantly know what kind of data a function expects and returns.
* **error detection:** static analysis tools like `mypy`, `pyright`, and `pylance` (used in vs code) can use type hints to detect type errors *before* you run your code. this catches bugs much earlier in the development process.
* **maintainability:** as your codebase grows, type hints become invaluable for refactoring and understanding complex interactions between different parts of your application. they act as a form of documentation that is automatically checked.
* **ide support:** many ides (e.g., vs code, pycharm) leverage type hints to provide better autocompletion, code navigation, and refactoring suggestions.
* **self-documenting code:** type hints reduce the need for verbose docstrings to describe the expected types of function arguments and return values. the type hints *are* the documentation.

**basic type hints**

the most fundamental type hints involve specifying the basic built-in types:

* `int`: integers (e.g., 10, -5, 0)
* `float`: floating-point numbers (e.g., 3.14, -2.5, 0.0)
* `str`: strings (e.g., "hello", "wo ...

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type hints
Python functions
function annotations
typing module
return type
static typing
function signatures
type checking
PEP 484
type hinting best practices
optional types
generics in Python
callable types
type hint examples
Python 3.5+