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Testing & modern typing

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

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How to Filter Data in Python with Type Hints

A reusable filter_data helper uses optional predicates and numeric bounds with modern Python type hints.

from typing import Iterable, TypeVar, Callable, Any

T = TypeVar("T")

def filter_data(
    items: Iterable[T],
    predicate: Callable[[T], bool] | None = None,
    *,
    min_value: float | None = None,
    max_value: float | None = None,
) -> list[T]:
    """Filter items by predicate and/or numeric bounds."""
    r…

11 0 Open

Testing & modern typing easy

How to Use Python Type Hints for Beginners

Build a data helper module with basic type hints — Union, Optional, List, Dict, Any, and TypeVar — to make your code clearer and safer.

type-hints typing annotations

Python

from typing import Any, Union, Optional, List, Dict, Tuple, Callable, TypeVar

T = TypeVar("T")

def describe(value: Any) -> str:
    """Return a human-readable description of the value's type."""
    if isinstance(value, list):
        return f"list of {len(value)} items"
    elif isinstance(value, dict):
        ret…

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Testing & modern typing easy

How to Validate Dataclass Fields with Python Type Hints

A beginner-friendly helper that checks if instance attributes match their declared type hints using dataclasses and get_type_hints.

dataclasses type-hints validation

Python

from typing import Any, TypeVar, get_type_hints
from dataclasses import dataclass

T = TypeVar("T")

@dataclass
class User:
    name: str
    age: int
    email: str

def validate_fields(obj: Any) -> dict[str, bool]:
    """Check if object attributes match declared type hints."""
    hints = get_type_hints(obj.__class…

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