Week 1：Python 语法速成（TypeScript 对照）

# ===== Python =====
x: str = "hello"          # 显式类型（和 TS 一样）
y = 42                    # 类型推断（和 TS 一样！）
z = 3.14                  # float
is_ok = True              # bool，注意大写 T！
items: list[int] = [1, 2, 3]
config: dict[str, any] = {"key": "value"}

# ===== TypeScript 对照 =====
// const x: string = "hello"
// const y = 42
// const z = 3.14
// const isOk = true
// const items: number[] = [1, 2, 3]
// const config: Record<string, any> = { key: "value" }

name = "Alice"
age = 25

# f-string = TS 的模板字符串 `${}`
greeting = f"Hello, {name}! You are {age} years old."

# 多行字符串（用三引号，和 JS 的模板字符串一样）
desc = """
这是一个
多行文本
"""

# ===== TS 对照 =====
// const greeting = `Hello, ${name}! You are ${age} years old.`
// const desc = `这是一个
// 多行文本`;

# ===== if/elif/else =====
score = 85
if score >= 90:
    grade = "A"
elif score >= 60:    # 注意是 elif，不是 else if
    grade = "B"
else:
    grade = "C"

# ===== for 循环 =====
fruits = ["apple", "banana", "cherry"]
for fruit in fruits:          # 相当于 TS 的 for...of
    print(f"水果: {fruit}")

# 带索引的遍历
for i, fruit in enumerate(fruits):
    print(f"{i}: {fruit}")

# ===== while 循环 =====
count = 0
while count < 5:
    count += 1
    print(count)

# ===== TS 对照 =====
// fruits.forEach((fruit, i) => console.log(`${i}: ${fruit}`))
// for (const fruit of fruits) { ... }
// while (count < 5) { count++; }

# ===== 基本函数 =====
def add(a: int, b: int) -> int:
    return a + b

# ===== 默认参数 =====
def greet(name: str, greeting: str = "Hello") -> str:
    return f"{greeting}, {name}!"

# ===== 关键字参数 =====
result = greet(greeting="Hi", name="World")  # 顺序可以换！

# ===== 不定参数 =====
def sum_all(*numbers: int) -> int:        # *args 接收多个位置参数
    return sum(numbers)

def print_config(**kwargs: any) -> None:  # **kwargs 接收多个命名参数
    for k, v in kwargs.items():
        print(f"{k} = {v}")

# ===== 返回 None =====
def log(msg: str) -> None:
    print(msg)

# ===== TS 对照 =====
// function add(a: number, b: number): number { return a + b; }
// function greet(name: string, greeting = "Hello"): string { ... }

# ===== dataclass（推荐！相当于 TS 的 interface + 自动构造函数）=====
from dataclasses import dataclass

@dataclass
class Todo:
    id: int
    text: str
    done: bool = False  # 默认值

# 使用
t = Todo(id=1, text="买牛奶")
print(t.text)        # 买牛奶
print(t)             # Todo(id=1, text='买牛奶', done=False) — 自动生成 __repr__

# ===== 传统类写法（了解即可）=====
class Animal:
    def __init__(self, name: str):    # 构造函数
        self.name = name              # self = this
    
    def speak(self) -> None:
        print(f"{self.name} says...")

class Dog(Animal):                     # 继承
    def speak(self) -> None:
        print(f"{self.name} says: Woof!")

# ===== TS 对照 =====
// interface Todo { id: number; text: string; done?: boolean }
// class Animal { constructor(public name: string) {} speak() {} }
// class Dog extends Animal { speak() {} }

# ===== 标准库导入 =====
import math                        # 整个模块
from datetime import datetime      # 只导入某个函数/类
from os import path as ospath      # 重命名

# ===== 第三方库导入（安装后）=====
from fastapi import FastAPI
from pydantic import BaseModel

# ===== 本地模块导入 =====
from my_package.my_module import my_func

# ===== TS 对照 =====
// import * as math from 'math'
// import { FastAPI } from 'fastapi'
// import { myFunc } from './my-module'

# ===== todo.py =====
from dataclasses import dataclass  # 相当于 TS 的 interface

@dataclass
class Todo:
    id: int
    text: str
    done: bool = False

todos: list[Todo] = []   # 相当于 const todos: Todo[] = []
next_id: int = 1         # snake_case 是 Python 规范

def add_todo(text: str) -> None:
    global next_id                              # Python 需要声明才能修改全局变量
    todos.append(Todo(id=next_id, text=text))   # 不用 new 关键字！
    next_id += 1
    print(f"✅ Added: {text}")                  # f-string = 模板字符串

def list_todos() -> None:
    for t in todos:                             # for...of 循环
        status = '✓' if t.done else '○'         # 三元运算符
        print(f"{status} {t.id}. {t.text}")

def toggle_todo(id: int) -> None:
    for todo in todos:                          # 相当于 Array.find()
        if todo.id == id:
            todo.done = not todo.done           # not = !
            break

# 测试
add_todo("学习 Python")
add_todo("写 FastAPI demo")
list_todos()
toggle_todo(1)
list_todos()