What are Generic types in Python?

Question

Accepted Answer

**Generic types** allow creating **reusable type-safe** classes and functions.

```python
from typing import TypeVar, Generic, Sequence

T = TypeVar("T")

class Stack(Generic[T]):
    def __init__(self) -> None:
        self._items: list[T] = []

def push(self, item: T) -> None:
        self._items.append(item)

def pop(self) -> T:
        return self._items.pop()

def peek(self) -> T:
        return self._items[-1]

# Typed stack
int_stack: Stack[int] = Stack()
int_stack.push(42)
value: int = int_stack.pop()  # Type-safe

str_stack: Stack[str] = Stack()
str_stack.push("hello")
```

**Multiple type variables:**
```python
K = TypeVar("K")
V = TypeVar("V")

class Registry(Generic[K, V]):
    def __init__(self) -> None:
        self._data: dict[K, V] = {}

def set(self, key: K, value: V) -> None:
        self._data[key] = value

def get(self, key: K) -> V | None:
        return self._data.get(key)
```

**Benefits:**
- Type safety at compile time.
- Better IDE support.
- Self-documenting code.

Python: What are Generic types in Python?