Type Hints

name: str = "Dave"
age: int = 30
price: float = 19.99
is_active: bool = True

age: int = "not a number"  # Python allows this

def create_user(name, email, age):
    # What types are these supposed to be?
    pass

def create_user(name: str, email: str, age: int) -> dict:
    # Crystal clear
    pass

# Strings - text
name: str = "Alice"
message: str = "Hello, world!"

# Integers - whole numbers
count: int = 42
user_id: int = 1001

# Floats - decimal numbers
price: float = 29.99
temperature: float = 98.6

# Booleans - true or false
is_active: bool = True
has_access: bool = False

# List of strings
tags: list[str] = ["python", "pydantic", "fastapi"]

# List of integers
quantities: list[int] = [1, 5, 3, 2]

# Dictionary with string keys and integer values
word_counts: dict[str, int] = {"error": 12, "warning": 5}

# Dictionary with string keys and string values
settings: dict[str, str] = {"theme": "dark", "language": "en"}

from typing import Optional

# These mean the same thing
middle_name: Optional[str] = None
middle_name: str | None = None

# User might not have a middle name
middle_name: str | None = None
middle_name: str | None = "James"

# Phone number is optional
phone: str | None = None
phone: str | None = "+1-555-0123"

from typing import Literal

status: Literal["draft", "published", "archived"] = "draft"

# Only these three values are valid
status = "draft"      # OK
status = "published"  # OK
status = "pending"    # Type checkers will warn about this

from typing import Literal

log_level: Literal["debug", "info", "warning", "error"] = "info"
priority: Literal["low", "medium", "high"] = "medium"
status: Literal["pending", "approved", "rejected"] = "pending"

def format_price(amount: float, currency: str = "USD") -> str:
    return f"{currency} {amount:.2f}"

def calculate_total(prices: list[float], tax_rate: float) -> float:
    subtotal = sum(prices)
    return subtotal * (1 + tax_rate)

def get_config(key: str) -> str | None:
    # Returns the config value if found, None if not
    pass

from typing import Optional, Literal

# Required string
name: str

# Optional string (can be None)
nickname: str | None = None

# String with default
country: str = "USA"

# List of items
items: list[str] = []

# Dictionary
metadata: dict[str, str] = {}

# Specific allowed values
role: Literal["admin", "user", "guest"] = "user"

age: int = "not a number"
prices: list[float] = "definitely not a list"