Introduction to Static Typing in Python

Python is a dynamically typed language, meaning you don't have to declare the type of a variable when you write your code. However, since Python 3.5, the language has supported optional static typing using type hints. Static typing can help catch errors early, improve code readability, and aid in code completion and linting by IDEs.

Basic Type Annotations

1. Variables

To specify the type of a variable, you can use a colon followed by the type.

age: int = 25
name: str = "Alice"
height: float = 5.7
is_student: bool = True

2. Functions

Type hints can also be used to specify the types of function arguments and return values.

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

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

3. Lists and Dictionaries

For more complex types like lists and dictionaries, you can use the typing module.

from typing import List, Dict

numbers: List[int] = [1, 2, 3]
grades: Dict[str, int] = {"Alice": 90, "Bob": 85}

4. Optional Types

If a variable can be of a certain type or None, use Optional.

from typing import Optional

def find_name(name_id: int) -> Optional[str]:
    # Simulated lookup
    if name_id == 1:
        return "Alice"
    return None

5. Union Types

When a variable can be multiple types, use Union.

from typing import Union

def get_value(value: Union[int, str]) -> str:
    return str(value)