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Testing & modern typing

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

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Design Data Helpers with Python TypedDict and Literal

Use TypedDict, Literal, and Union to define typed data shapes and parse values in Python.

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

class User(TypedDict):
    name: str
    age: int
    role: Literal["admin", "user", "guest"]

def describeUser(data: User) -> str:
    return f"{data['name']} ({data['age']}) — {data['role']}"

def parse_value(item: Union[int, str, None]) -> str:
    if it…

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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 Use Union Type Hints in Python

This code demonstrates how to use Union type hints to specify that a parameter can accept multiple types (int, float, str) and handle them accordingly.

type-hints union typing

Python

from typing import Union

def process_value(value: Union[int, float, str]) -> str:
    if isinstance(value, (int, float)):
        return f"Number: {value * 2}"
    return f"String: {value.upper()}"

if __name__ == "__main__":
    print(process_value(10))
    print(process_value(3.14))
    print(process_value("hello"))

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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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