python# 经典Hello Worlddef hello_world():"""这是一个文档字符串示例"""print("Hello, Python3!")if __name__ == "__main__":hello_world()

bashpython3 hello.py# 或使用交互式解释器python3>>> print("Hello from REPL!")

python# 数值类型x = 42          # 整数y = 3.14        # 浮点数z = 2 + 3j      # 复数# 布尔类型is_active = True# 字符串（支持Unicode）greeting = "你好，世界"multi_line = """这是多行字符串"""# 类型检查print(type(x))  # <class 'int'>

python# 列表（可变有序序列）fruits = ["apple", "banana", "cherry"]fruits.append("orange")print(fruits[1:3])  # 切片操作 ['banana', 'cherry']# 元组（不可变有序序列）coordinates = (10.0, 20.0)# 字典（键值对集合）person = {"name": "Alice","age": 30,"skills": ["Python", "SQL"]}# 集合（唯一元素集合）unique_numbers = {1, 2, 2, 3}  # 自动去重 {1, 2, 3}

python# 算术运算符result = (10 + 3) * 2 ** 3  # 104# 比较运算符is_equal = (5 == 5.0)  # True (值相等)# 逻辑运算符is_valid = True and (False or not True)# 成员运算符print("apple" in fruits)  # True# 三元表达式max_value = x if x > y else y

pythonage = 25if age < 13:print("儿童")elif age < 20:print("青少年")else:print("成人")

python# for循环（遍历序列）for fruit in fruits:print(f"我喜欢{fruit}")  # f-string格式化# while循环count = 0while count < 5:print(count)count += 1else:print("循环正常结束")# 循环控制for i in range(10):if i % 2 == 0:continue  # 跳过偶数if i > 7:break     # 提前终止print(i)

python# 基本函数def calculate_area(width, height=10):  # 默认参数"""计算矩形面积Args:width: 宽度（必须）height: 高度（可选，默认10）Returns:面积值"""return width * height# 可变参数def sum_all(*numbers):total = 0for num in numbers:total += numreturn total# 关键字参数def create_user(**details):print(f"创建用户: {details['name']}, 年龄: {details.get('age', '未知')}")# 调用示例print(calculate_area(5))          # 50print(sum_all(1, 2, 3, 4))       # 10create_user(name="Bob", age=25)   # 创建用户: Bob, 年龄: 25

pythonclass Animal:"""动物基类"""# 类属性species = "哺乳动物"def __init__(self, name, age):"""构造函数"""self.name = name  # 实例属性self.age = agedef make_sound(self):"""实例方法"""print("动物发出声音")@classmethoddef get_species(cls):"""类方法"""return cls.species@staticmethoddef is_adult(age):"""静态方法"""return age >= 18# 继承示例class Dog(Animal):def __init__(self, name, age, breed):super().__init__(name, age)self.breed = breeddef make_sound(self):print("汪汪汪！")# 使用示例dog = Dog("旺财", 3, "金毛")print(dog.name)          # 旺财dog.make_sound()         # 汪汪汪！print(Animal.get_species())  # 哺乳动物print(Animal.is_adult(20))   # True

pythonclass Vector:def __init__(self, x, y):self.x = xself.y = y# 重载加法运算符def __add__(self, other):return Vector(self.x + other.x, self.y + other.y)# 字符串表示def __str__(self):return f"Vector({self.x}, {self.y})"# 用于len()函数def __len__(self):return 2  # 二维向量v1 = Vector(1, 2)v2 = Vector(3, 4)print(v1 + v2)  # Vector(4, 6)print(len(v1))  # 2

python# 写入文件with open("example.txt", "w", encoding="utf-8") as f:f.write("第一行文本\n")f.writelines(["第二行\n", "第三行\n"])# 读取文件try:with open("example.txt", "r", encoding="utf-8") as f:# 读取全部内容content = f.read()print(content)# 逐行读取f.seek(0)  # 回到文件开头for line in f:print(f"行内容: {line.strip()}")except FileNotFoundError:print("文件不存在！")

pythondef divide(a, b):try:result = a / bexcept ZeroDivisionError:print("错误：除数不能为零")return Noneexcept TypeError as e:print(f"类型错误: {e}")return Noneelse:print("计算成功")finally:print("执行清理操作")return resultprint(divide(10, 2))  # 5.0print(divide(10, 0))  # 错误提示

pythonfrom datetime import datetime, timedelta# 当前时间now = datetime.now()print(now.strftime("%Y-%m-%d %H:%M:%S"))  # 2023-05-20 14:30:45# 时间计算future = now + timedelta(days=7)print(f"一周后: {future.date()}")# 解析时间字符串date_str = "2023-05-20"parsed_date = datetime.strptime(date_str, "%Y-%m-%d")print(parsed_date.weekday())  # 星期几（0=周一）

pythonimport jsondata = {"name": "张三","age": 30,"skills": ["Python", "Java"],"married": False}# 序列化为JSON字符串json_str = json.dumps(data, indent=4, ensure_ascii=False)print(json_str)# 写入JSON文件with open("data.json", "w", encoding="utf-8") as f:json.dump(data, f, indent=2, ensure_ascii=False)# 从JSON字符串解析parsed_data = json.loads(json_str)print(parsed_data["skills"][0])  # Python

pythonimport retext = "我的电话是138-1234-5678，另一个是139*9876*5432"# 查找所有电话号码pattern = r"\d{3}[-*]\d{4}[-*]\d{4}"matches = re.findall(pattern, text)print(matches)  # ['138-1234-5678', '139*9876*5432']# 替换敏感信息cleaned = re.sub(r"\d{3}[-*]\d{4}[-*]\d{4}", "***-****-****", text)print(cleaned)  # 我的电话是***-****-****，另一个是***-****-****

pythonclass StudentManagementSystem:def __init__(self):self.students = []def add_student(self):name = input("请输入学生姓名: ")age = int(input("请输入学生年龄: "))score = float(input("请输入学生成绩: "))student = {"name": name,"age": age,"score": score}self.students.append(student)print(f"成功添加学生: {name}")def find_students(self):keyword = input("请输入搜索关键词(姓名/年龄): ")results = []try:age = int(keyword)results = [s for s in self.students if s["age"] == age]except ValueError:results = [s for s in self.students if keyword.lower() in s["name"].lower()]self.display_students(results)def display_students(self, students=None):if students is None:students = self.studentsif not students:print("没有找到学生记录")returnprint("\n学生列表:")print("-" * 40)print(f"{'姓名':<10}{'年龄':<8}{'成绩':<8}")print("-" * 40)for s in students:print(f"{s['name']:<10}{s['age']:<8}{s['score']:<8.1f}")def save_to_file(self):with open("students.json", "w", encoding="utf-8") as f:json.dump(self.students, f, indent=2, ensure_ascii=False)print("数据已保存到文件")def load_from_file(self):try:with open("students.json", "r", encoding="utf-8") as f:self.students = json.load(f)print("数据已从文件加载")except FileNotFoundError:print("没有找到数据文件，将创建新系统")def main():sms = StudentManagementSystem()sms.load_from_file()while True:print("\n学生管理系统")print("1. 添加学生")print("2. 查找学生")print("3. 显示所有学生")print("4. 保存数据")print("5. 退出系统")choice = input("请选择操作(1-5): ")if choice == "1":sms.add_student()elif choice == "2":sms.find_students()elif choice == "3":sms.display_students()elif choice == "4":sms.save_to_file()elif choice == "5":sms.save_to_file()print("感谢使用，再见！")breakelse:print("无效输入，请重新选择")if __name__ == "__main__":main()