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Testing & modern typing

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

3 matches

How to Use TypedDict for Data Validation in Python

Define a TypedDict schema and validate raw dictionary input with type hints for safer, more readable data handling.

from typing import Any, Dict, List, Optional, Union, TypedDict, Literal

class Product(TypedDict):
    product_id: int
    name: str
    price: Union[int, float]
    in_stock: bool
    tags: Optional[List[str]]

def validate_product(data: Dict[str, Any]) -> Product:
    product_id: int = int(data["product_id"])
    na…

15 0 Open

Testing & modern typing medium

How to Validate Data in Python with Typing Hints

Build a runtime validation helper that checks values against Python type hints like Optional, list, and basic types.

typing validation type-hints

Python

from typing import Any, Optional, Union, TypeVar, get_origin, get_args

T = TypeVar("T")

def validate(value: Any, expected_type: type) -> Optional[str]:
    """Returns an error message if value doesn't match expected_type, else None."""
    # Handle Optional[...] types
    origin = get_origin(expected_type)
    if or…

14 0 Open

Testing & modern typing medium

Use pytest fixture to mock a database connection in Python

This code shows how to use a pytest fixture and unittest.mock to replace a database connection with a Mock, enabling isolated tests without a real database.

pytest fixtures unittest.mock

Python

import pytest
import sqlite3
from unittest.mock import Mock

class Database:
    def __init__(self, connection):
        self.connection = connection

    def get_user(self, user_id):
        cursor = self.connection.cursor()
        cursor.execute("SELECT * FROM users WHERE id = ?", (user_id,))
        return cursor.…

19 0 Open

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