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Testing & modern typing

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

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How to Convert Strings to Types in Python Using TypeVar

A beginner-friendly helper that converts a string to int, float, bool, or str with type hints and graceful failure handling.

typing type-hints conversion

Python

from typing import TypeVar, Optional

T = TypeVar("T")

def convert_data(value: str, target_type: type[T]) -> Optional[T]:
    """Convert string value to target type; return None on failure."""
    try:
        if target_type is int:
            return int(value)
        elif target_type is float:
            return f…

14 0 Open

Testing & modern typing easy

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.

filtering type-hints generics

Python

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…

12 0 Open

Testing & modern typing easy

How to Sort Data in Python

Sort sequences with type-safe helpers that handle mixed data with a string fallback.

sorting typing protocol

Python

from typing import Any, TypeVar, Protocol, Sequence, Iterable

T = TypeVar("T")
Comparable = TypeVar("Comparable", bound="Comparable")

class Sortable(Protocol):
    def __lt__(self, other: Any) -> bool: ...

S = TypeVar("S", bound=Sortable)

def sort_data(data: Sequence[S], *, reverse: bool = False) -> list[S]:
    "…

14 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…

13 0 Open

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