什麼是Python中的類型暗示？

類型提示在Python中用於表明變量、函數參數或返回值的預期類型，但不強制執行。它使代碼更清晰易懂，尤其適用於大型項目或團隊協作。使用類型提示的原因包括提高代碼可讀性、借助工具（如mypy）及早發現潛在錯誤、改善編輯器自動補全建議。類型提示是可選的，不影響代碼運行方式。添加變量類型提示的方法是在變量名後使用冒號（:），例如age: int = 25和name: str = "Alice"。常見基本類型有int、float、str、list、dict、tuple、bool和None。對於函數，可在參數和返回值上添加類型提示，如def greet(name: str) -> str:。無返回值的函數應指定為-> None。若參數可能為多個類型，可使用typing模塊的Union，如Union[int, str]。列表和字典等容器類型需指定其內容類型，如list[str]和dict[str, int]。舊版本Python需從typing導入List、Dict等。若函數可能返回值或無值，應使用Optional，如Optional[dict]。總之，類型提示雖非必需，但有助於減少錯誤並提升協作效率。

Type hinting in Python is a way to indicate what type of data a variable, function argument, or return value is expected to be, without enforcing it. It helps make code clearer and easier to understand, especially in larger projects or when working with others.

Why Use Type Hints?

Python is dynamically typed, which means you don't have to declare types when writing code. But that flexibility can sometimes lead to confusion or bugs. Type hints help by:

• Making the code more readable
• Catching potential errors early (with tools like mypy)
• Improving autocomplete suggestions in editors

They're optional — your code still runs the same way whether or not you use them.

How to Add Type Hints to Variables

You can add type hints to variables right after their name using a colon ( : ). For example:

 age: int = 25
name: str = "Alice"

This tells anyone reading the code (and tools) that age should be an integer and name should be a string. If you assign a wrong type later, Python won't stop you — but static type checkers might warn you.

Some common types you'll see:

• int , float , str
• list , dict , tuple
• bool , None

Adding Type Hints to Functions

Functions are where type hints become really useful. You can specify the types of arguments and the return type using an arrow ( -> ):

 def greet(name: str) -> str:
    return f"Hello, {name}"

This says: the function greet takes a string as input and returns a string. Again, Python doesn't enforce this, but it makes the function's purpose clearer.

For functions that don't return anything, use None :

 def log_message(message: str) -> None:
    print(message)

If a function uses multiple types for an argument, you can use Union from the typing module:

 from typing import Union

def process(value: Union[int, str]) -> None:
    ...

Basic Types and Common Tools

The built-in types like list , dict , and tuple work with type hints too, but you need to specify what they contain. For example:

 names: list[str] = ["Alice", "Bob"]
user: dict[str, int] = {"age": 30}

These examples say that names contains only strings, and user is a dictionary with string keys and integer values.

Older versions of Python (before 3.9) require you to import these from the typing module like List , Dict , etc.

Also, if something can be either a value or nothing, use Optional :

 from typing import Optional

def find_user(user_id: int) -> Optional[dict]:
    ...

That means the function may return a dictionary or None .

基本上就這些。 Type hinting isn't required, but once you start using it, you'll probably notice fewer bugs and smoother collaboration.

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