if 條件表達式：
    語句組

# 檢查一個數(shù)是否為正數(shù)
num = 10
if num > 0:
    print("這是一個正數(shù)")

這是一個正數(shù)

# 檢查一個人是否滿足參加某活動的條件
age = 25
is_student = True

if age >= 18 and is_student:
    print("您滿足參加活動的條件")

您滿足參加活動的條件

if 條件表達式:
    語句組1  # 條件為True時執(zhí)行
else:
    語句組2  # 條件為False時執(zhí)行

# 判斷一個數(shù)是奇數(shù)還是偶數(shù)
num = 15
if num % 2 == 0:
    print(f"{num}是偶數(shù)")
else:
    print(f"{num}是奇數(shù)")

15是奇數(shù)

# 簡單的用戶登錄驗證
username = "admin"
password = "12345"

input_username = "admin"
input_password = "12345"

if username == input_username and password == input_password:
    print("登錄成功！歡迎回來。")
else:
    print("用戶名或密碼錯誤，請重試。")

登錄成功！歡迎回來。

if 條件表達式1:
    語句組1  # 條件1為True時執(zhí)行
elif 條件表達式2:
    語句組2  # 條件1為False且條件2為True時執(zhí)行
elif 條件表達式3:
    語句組3  # 條件1和2為False且條件3為True時執(zhí)行
...
else:
    語句組n  # 所有條件都為False時執(zhí)行

# 根據(jù)分數(shù)給出評級
score = 85

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

print(f"分數(shù)為{score}，評級為{grade}")

分數(shù)為85，評級為B

# 根據(jù)月份判斷季節(jié)（北半球）
month = 7

if month in [12, 1, 2]:
    season = "冬季"
elif month in [3, 4, 5]:
    season = "春季"
elif month in [6, 7, 8]:
    season = "夏季"
elif month in [9, 10, 11]:
    season = "秋季"
else:
    season = "輸入月份有誤"

print(f"{month}月是{season}")

7月是夏季

# 嵌套條件語句示例 - 簡單計算器
num1 = 10
num2 = 5
operation = "+"

if operation == "+":
    result = num1 + num2
elif operation == "-":
    result = num1 - num2
elif operation == "*":
    result = num1 * num2
elif operation == "/":
    if num2 == 0:  # 嵌套條件語句
        print("錯誤：除數(shù)不能為零")
        result = "未定義"
    else:
        result = num1 / num2
else:
    print("不支持的操作")
    result = "未定義"

print(f"{num1} {operation} {num2} = {result}")

10 + 5 = 15

value_if_true if condition else value_if_false

# 使用條件表達式判斷大小
a = 10
b = 20
maximum = a if a > b else b
print(f"較大的數(shù)是: {maximum}")

較大的數(shù)是: 20

# 簡單的登錄系統(tǒng)
def login_system():
    # 預設的用戶信息
    users = {
        "admin": "admin123",
        "user1": "password1",
        "user2": "password2"
    }
    
    username = input("請輸入用戶名: ")
    password = input("請輸入密碼: ")
    
    if username in users:
        if users[username] == password:
            print(f"歡迎回來，{username}！")
        else:
            print("密碼錯誤！")
    else:
        print("用戶不存在！")
        register = input("是否要注冊新用戶？(yes/no): ")
        if register.lower() == "yes":
            print("注冊功能正在開發(fā)中...")
        else:
            print("感謝使用，再見！")

# 調(diào)用函數(shù)
# login_system()  # 取消注釋以運行交互式登錄系統(tǒng)

import random

def guess_number_game():
    # 生成1-100之間的隨機數(shù)
    target = random.randint(1, 100)
    attempts = 0
    max_attempts = 7
    
    print("歡迎參加猜數(shù)字游戲！")
    print(f"我已經(jīng)想好了一個1-100之間的數(shù)字，你有{max_attempts}次機會猜出它。")
    
    while attempts < max_attempts:
        try:
            guess = int(input("請輸入你的猜測: "))
            attempts += 1
            
            if guess < 1 or guess > 100:
                print("請輸入1-100之間的數(shù)字！")
                continue
                
            if guess < target:
                print("太小了！")
            elif guess > target:
                print("太大了！")
            else:
                print(f"恭喜你，猜對了！答案就是{target}。")
                print(f"你用了{attempts}次嘗試。")
                break
                
            if attempts < max_attempts:
                print(f"你還有{max_attempts - attempts}次機會。")
            
        except ValueError:
            print("請輸入有效的數(shù)字！")
    
    if attempts == max_attempts and guess != target:
        print(f"游戲結束！正確答案是{target}。")

# 調(diào)用函數(shù)
# guess_number_game()  # 取消注釋以運行猜數(shù)字游戲