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我来为你介绍几个Python条件判断的实用案例,从基础到进阶：
基础条件判断案例
案例1：判断成绩等级
# 根据分数判断等级
score = int(input("请输入成绩（0-100）："))
if score >= 90:
print("优秀")
elif score >= 80:
print("良好")
elif score >= 70:
print("中等")
elif score >= 60:
print("及格")
else:
print("不及格")
# 更严谨的写法，包含输入验证
if 0 <= score <= 100:
if score >= 90:
print("优秀")
elif score >= 80:
print("良好")
elif score >= 70:
print("中等")
elif score >= 60:
print("及格")
else:
print("不及格")
else:
print("请输入0-100之间的分数")
案例2：判断闰年
year = int(input("请输入年份："))
# 判断闰年条件：能被4整除但不能被100整除，或者能被400整除
if (year % 4 == 0 and year % 100 != 0) or (year % 400 == 0):
print(f"{year}年是闰年")
else:
print(f"{year}年是平年")
实用案例
案例3：登录验证系统
# 模拟登录验证
username = input("请输入用户名：")
password = input("请输入密码：")
# 预设的用户名和密码
correct_username = "admin"
correct_password = "123456"
# 条件判断
if username == correct_username and password == correct_password:
print("登录成功！欢迎回来")
elif username != correct_username:
print("用户名错误")
elif password != correct_password:
print("密码错误")
else:
print("登录失败")
案例4：温度转换与提示
temperature = float(input("请输入温度："))
unit = input("请输入温度单位 (C/F)：").upper()
if unit == "C":
# 摄氏度转华氏度
fahrenheit = (temperature * 9/5) + 32
print(f"{temperature}°C = {fahrenheit:.1f}°F")
# 温度提示
if temperature >= 35:
print("⚠️ 高温预警！注意防暑")
elif temperature >= 25:
print("☀️ 天气炎热，适合游泳")
elif temperature >= 15:
print("🌤️ 天气舒适，适合户外活动")
elif temperature >= 5:
print("🌥️ 天气凉爽，注意添衣")
else:
print("❄️ 天气寒冷，注意保暖")
elif unit == "F":
# 华氏度转摄氏度
celsius = (temperature - 32) * 5/9
print(f"{temperature}°F = {celsius:.1f}°C")
else:
print("请输入正确的温度单位 (C 或 F)")
复杂业务逻辑案例
案例5：购物折扣计算器
# 根据购买金额和会员等级计算折扣
total_amount = float(input("请输入购物总金额："))
membership = input("请输入会员等级 (普通/银卡/金卡/钻石)：")
# 判断折扣
if total_amount >= 1000:
if membership == "钻石":
discount = 0.7 # 7折
points = total_amount * 2 # 双倍积分
elif membership == "金卡":
discount = 0.8 # 8折
points = total_amount * 1.5
elif membership == "银卡":
discount = 0.85 # 85折
points = total_amount * 1.2
else:
discount = 0.9 # 9折
points = total_amount
elif total_amount >= 500:
if membership == "钻石":
discount = 0.75
points = total_amount * 1.8
elif membership == "金卡":
discount = 0.85
points = total_amount * 1.3
elif membership == "银卡":
discount = 0.9
points = total_amount * 1.1
else:
discount = 0.95
points = total_amount
else:
if membership == "钻石":
discount = 0.8
points = total_amount * 1.5
elif membership == "金卡":
discount = 0.88
points = total_amount * 1.2
else:
discount = 1.0 # 不打折
points = total_amount
final_amount = total_amount * discount
print(f"原价：¥{total_amount:.2f}")
print(f"折扣：{int((1-discount)*100)}%")
print(f"实付：¥{final_amount:.2f}")
print(f"获得积分：{int(points)}")
案例6：BMI健康评估系统
# 计算BMI指数并给出健康建议
height = float(input("请输入身高（米）："))
weight = float(input("请输入体重（公斤）："))
# 计算BMI
bmi = weight / (height ** 2)
print(f"您的BMI指数为：{bmi:.1f}")
# 判断健康状况
if bmi < 18.5:
print("⚠️ 体重过轻")
advice = "建议增加营养摄入，适当锻炼增肌"
elif bmi < 24:
print("✅ 体重正常")
advice = "请保持健康的饮食习惯和运动"
elif bmi < 28:
print("⚠️ 超重")
advice = "建议控制饮食，增加运动量"
elif bmi < 32:
print("❌ 肥胖（一级）")
advice = "建议专业健康指导，合理饮食配合运动"
elif bmi < 37:
print("❌ 肥胖（二级）")
advice = "建议咨询医生，制定科学的减重计划"
else:
print("‼️ 极度肥胖（三级）")
advice = "强烈建议寻求医疗帮助，进行专业干预"
print(f"健康建议：{advice}")
简化代码技巧
使用三元运算符
# 传统写法
age = 20
if age >= 18:
status = "成年"
else:
status = "未成年"
# 三元运算符写法
status = "成年" if age >= 18 else "未成年"
使用字典优化条件判断
# 代替多个if-elif
def get_day_name(day_number):
days = {
1: "星期一",
2: "星期二",
3: "星期三",
4: "星期四",
5: "星期五",
6: "星期六",
7: "星期日"
}
return days.get(day_number, "无效的输入")
print(get_day_name(3)) # 输出：星期三
编写建议
- 按照优先级排序：把最可能满足的条件放在前面，提高效率
- 使用括号明确优先级：复杂条件用括号分组，提高可读性
- 避免过深的嵌套：嵌套超过3层时，考虑重构
- 保持条件互斥：确保else分支能覆盖所有未处理的情况
- 输入验证：对用户输入进行合法性检查
这些案例覆盖了从基础到实用的Python条件判断场景,你可以根据实际需求进行调整和组合使用。
