# 哪些東西自帶布爾值？先記住這幾個(gè)
print(bool(0))        # False
print(bool(1))        # True
print(bool(""))       # False
print(bool("abc"))    # True
print(bool([]))       # False
print(bool([1, 2]))   # True
print(bool(None))     # False

age = 20
print(age >= 18)    # True
print(age == 18)    # False
print(age != 18)    # True

score = 85
if 80 <= score < 90:
    print("良好")    # 這下會(huì)打印

age = int(input("輸入年齡: "))

if age >= 18:
    print("你已經(jīng)成年了")
    print("可以去考駕照了")

# 這樣寫會(huì)報(bào)錯(cuò)
if age >= 18:
    print("成年了")
  print("這行縮進(jìn)不對")    # IndentationError

# 看起來一樣，但一個(gè)用了空格一個(gè)用了Tab
if True:
    print("這行用了4個(gè)空格")
	print("這行用了Tab")   # 肉眼看不出來，但運(yùn)行報(bào)錯(cuò)

score = 78

if score >= 90:
    grade = "A"
elif score >= 80:
    grade = "B"
elif score >= 70:
    grade = "C"
elif score >= 60:
    grade = "D"
else:
    grade = "E"

print(f"等級: {grade}")    # C

# 畫蛇添足
if score >= 90:
    grade = "A"
if score >= 80 and score < 90:    # 其實(shí)不需要 and score < 90
    grade = "B"
if score >= 70 and score < 80:
    grade = "C"

# 用戶輸入用戶名，沒輸入就給個(gè)默認(rèn)名
username = input("請輸入用戶名: ")
if username.strip() == "":
    username = "游客"
else:
    print(f"歡迎回來, {username}")

import re

phone = input("輸入手機(jī)號: ")
if re.match(r'^1[3-9]\d{9}$', phone):
    print("手機(jī)號格式正確")
else:
    print("手機(jī)號格式有誤，請重新輸入")

# 查找列表中是否有某個(gè)元素
items = [1, 2, 3, 4, 5]
target = 6

for item in items:
    if item == target:
        print("找到了！")
        break
else:
    print("沒找到")    # 循環(huán)沒有被break，執(zhí)行這里

age = 25
has_license = True

if age >= 18:
    if has_license:
        print("可以租車")
    else:
        print("需要先考駕照")
else:
    print("未成年不能租車")

if age >= 18 and has_license:
    print("可以租車")
elif age >= 18 and not has_license:
    print("需要先考駕照")
else:
    print("未成年不能租車")

# 三層嵌套，看五分鐘不知道在干嘛
if condition1:
    if condition2:
        if condition3:
            do_something()
        else:
            do_other()
    else:
        do_third()
else:
    do_fourth()

# and 短路：左邊為False，右邊根本不會(huì)執(zhí)行
def expensive_check():
    print("這個(gè)函數(shù)執(zhí)行了")
    return True

if False and expensive_check():
    print("不會(huì)打印")
# "這個(gè)函數(shù)執(zhí)行了" 不會(huì)打印，因?yàn)樽筮叺腇alse已經(jīng)讓整個(gè)and確定為False了

# or 短路：左邊為True，右邊不執(zhí)行
if True or expensive_check():
    print("會(huì)打印")
# "這個(gè)函數(shù)執(zhí)行了" 不會(huì)打印

# 安全地獲取嵌套字典的值
user = {"profile": {"name": "張三"}}
if user and user.get("profile") and user["profile"].get("name"):
    print(user["profile"]["name"])

# 用短路特性簡化
name = user and user.get("profile") and user["profile"].get("name")
# 如果中間某個(gè)不存在，name就是False（或None），不會(huì)報(bào)錯(cuò)

# 如果用戶沒輸入名字，用默認(rèn)值
name = input("輸入名字: ") or "匿名用戶"
print(name)

age = 20
status = "成年" if age >= 18 else "未成年"
print(status)    # 成年

# 取最大值
a, b = 10, 20
max_val = a if a > b else b

# 格式化輸出
price = 99.9
tip = "需要配送費(fèi)" if price < 100 else "免配送費(fèi)"

# 讓人看不懂的寫法
result = a if a > b else b if b > c else c    # 雖然能跑

# 換成if-elif-else，三秒鐘就看懂了
if a > b and a > c:
    result = a
elif b > c:
    result = b
else:
    result = c

# 不用寫成 if len(name) > 0
name = "張三"
if name:
    print(f"你好, {name}")
else:
    print("名字不能為空")

# 不用寫成 if len(items) != 0
items = [1, 2, 3]
if items:
    print(f"有{len(items)}個(gè)項(xiàng)目")

# 不用寫成 if user is not None and user != {}
user = {"name": "張三"}
if user:
    print(user["name"])

if name == True:      # 多此一舉
if items != []:       # 雖然能跑但不Pythonic
if len(name) > 0:     # 可以但啰嗦

# 錯(cuò)誤
if age > 18:
print("成年了")    # 縮進(jìn)沒對齊

# 如果暫時(shí)不想寫邏輯，用pass占位
if age > 18:
    pass    # pass就是啥也不做，占位用的

import re

def validate_username(username):
    """用戶名：3-12位，字母數(shù)字下劃線"""
    if not username:
        return False, "用戶名不能為空"
    if len(username) < 3 or len(username) > 12:
        return False, "用戶名長度需為3-12位"
    if not re.match(r'^[a-zA-Z0-9_]+$', username):
        return False, "用戶名只能包含字母、數(shù)字、下劃線"
    return True, "用戶名可用"

def validate_password(password, confirm):
    """密碼：至少8位，包含字母和數(shù)字"""
    if not password:
        return False, "密碼不能為空"
    if len(password) < 8:
        return False, "密碼至少8位"
    if not re.search(r'[a-zA-Z]', password):
        return False, "密碼需要包含字母"
    if not re.search(r'\d', password):
        return False, "密碼需要包含數(shù)字"
    if password != confirm:
        return False, "兩次輸入的密碼不一致"
    return True, "密碼可用"

def validate_email(email):
    """郵箱：簡單格式驗(yàn)證"""
    if not email:
        return False, "郵箱不能為空"
    if not re.match(r'^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\.[a-zA-Z]{2,}$', email):
        return False, "郵箱格式不正確"
    return True, "郵箱格式正確"

def main():
    print("=" * 40)
    print("用戶注冊信息驗(yàn)證")
    print("=" * 40)
    
    # 收集用戶輸入
    username = input("用戶名: ").strip()
    password = input("密碼: ").strip()
    confirm = input("確認(rèn)密碼: ").strip()
    email = input("郵箱: ").strip()
    
    # 逐項(xiàng)驗(yàn)證，只要有一項(xiàng)失敗就停止
    valid, msg = validate_username(username)
    if not valid:
        print(f"? {msg}")
        return
    
    valid, msg = validate_password(password, confirm)
    if not valid:
        print(f"? {msg}")
        return
    
    valid, msg = validate_email(email)
    if not valid:
        print(f"? {msg}")
        return
    
    # 所有驗(yàn)證通過
    print("? 所有信息驗(yàn)證通過！")
    print(f"用戶名: {username}")
    print(f"郵箱: {email}")
    print("密碼: ********")

if __name__ == "__main__":
    main()