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Testing & modern typing

pytest basics, mocks, type hints, TypedDict, Protocol, and static-checking patterns.

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How to Group Data by Key in Python with Type Hints

Group a list of dictionaries by a specified key using a typed helper function and print a summary of each group.

from typing import Any, Dict, List, TypeVar, Union

T = TypeVar("T")

def group_by(data: List[Dict[str, Any]], key: str) -> Dict[Any, List[Dict[str, Any]]]:
    """Group a list of dictionaries by a given key."""
    grouped: Dict[Any, List[Dict[str, Any]]] = {}
    for item in data:
        value = item.get(key)
     …

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Testing & modern typing easy

How to Merge TypedDicts in Python

Merge two TypedDict dictionaries with type-aware logic using NotRequired, **kwargs unpacking, and safe key updates.

typing typeddict dict

Python

from typing import TypedDict, NotRequired, merge  # hypothetical

class User(TypedDict):
    name: str
    email: NotRequired[str]
    age: NotRequired[int]

def merge_users(base: User, **overrides: User) -> User:
    """Merge two user dicts with typing-aware logic."""
    result: User = dict(base)
    for key, value …

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Testing & modern typing easy

How to Use TypedDict for Structured Dict Typing in Python

Define and use TypedDict to add type hints to dictionaries, improving code clarity and enabling static type checking in your Python projects.

typing typeddict type-hints

Python

from typing import TypedDict


class User(TypedDict):
    name: str
    age: int
    email: str


def greet(user: User) -> str:
    return f"Hello {user['name']}, age {user['age']}, contact {user['email']}"


if __name__ == "__main__":
    alice: User = {"name": "Alice", "age": 30, "email": "alice@example.com"}
    pr…

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