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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…

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Testing & modern typing easy

How to Parse Data with Type Hints in Python

A beginner-friendly helper that parses simple dictionary- or list-like strings into typed Python structures using modern typing annotations.

type-hints parsing typing

Python

from typing import Any, Dict, List, Union


def parse_data(raw: str) -> Union[Dict[str, Any], List[Any], str]:
    """Parse a simple string into structured data using type hints."""
    cleaned = raw.strip()
    
    if not cleaned:
        return {}
    
    if cleaned.startswith("{") and cleaned.endswith("}"):
     …

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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]:
    "…

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Testing & modern typing easy

How to Use Literal Type Hints in Python

Use typing.Literal to restrict a function parameter to specific allowed string values and get static type checking.

typing type-hints literal

Python

from typing import Literal

def get_status_message(status: Literal["active", "inactive", "pending"]) -> str:
    """Return a message based on the status value."""
    if status == "active":
        return "Account is active"
    elif status == "inactive":
        return "Account is inactive"
    else:
        return "…

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Testing & modern typing easy

How to use Optional type hint in Python

Use the Optional type hint to indicate a parameter can be a string or None, with an example function that handles both cases.

typing optional type-hints

Python

from typing import Optional

def greet(name: Optional[str]) -> str:
    if name is None:
        return "Hello, anonymous!"
    else:
        return f"Hello, {name}!"

if __name__ == "__main__":
    print(greet("Alice"))
    print(greet(None))

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