字典操作示例

# 创建字典的多种方式
# 1. 使用花括号
student = {
    'name': '张三',
    'age': 18,
    'score': 95
}

# 2. 使用dict()构造函数
person = dict(name='李四', age=20, city='北京')

# 3. 使用zip()创建字典
keys = ['a', 'b', 'c']
values = [1, 2, 3]
letter_dict = dict(zip(keys, values))

# 访问字典元素
print(student['name'])      # 输出: 张三
print(person.get('age'))    # 输出: 20
print(person.get('phone', '未设置'))  # 使用默认值，输出: 未设置
                        

student = {'name': '张三', 'age': 18, 'score': 95}

# 修改值
student['age'] = 19
student['score'] = 98

# 添加新键值对
student['class'] = '三年二班'

# 删除键值对
del student['score']
removed_age = student.pop('age')
last_item = student.popitem()  # 删除并返回最后一个键值对

print(student)  # 输出: {'name': '张三'}
print(f"移除的年龄: {removed_age}")  # 输出: 移除的年龄: 19
print(f"最后移除的项: {last_item}")  # 输出: 最后移除的项: ('class', '三年二班')
                        

student = {'name': '张三', 'age': 18, 'score': 95}

# 获取所有键
keys = student.keys()
print("所有键:", list(keys))  # ['name', 'age', 'score']

# 获取所有值
values = student.values()
print("所有值:", list(values))  # ['张三', 18, 95]

# 获取所有键值对
items = student.items()
print("所有键值对:", list(items))  # [('name', '张三'), ('age', 18), ('score', 95)]

# 更新字典
new_info = {'phone': '123456', 'email': '[email protected]'}
student.update(new_info)
print("更新后:", student)

# 清空字典
student.clear()
print("清空后:", student)  # {}
                        

# 创建平方数字典
squares = {x: x**2 for x in range(5)}
print(squares)  # {0: 0, 1: 1, 2: 4, 3: 9, 4: 16}

# 过滤字典
scores = {'张三': 85, '李四': 92, '王五': 78, '赵六': 95}
high_scores = {name: score for name, score in scores.items() if score >= 90}
print(high_scores)  # {'李四': 92, '赵六': 95}

# 键值互换
original = {'a': 1, 'b': 2, 'c': 3}
inverted = {value: key for key, value in original.items()}
print(inverted)  # {1: 'a', 2: 'b', 3: 'c'}
                        

# 创建嵌套字典
school = {
    'class_1': {
        '张三': {'age': 18, 'score': 95},
        '李四': {'age': 17, 'score': 89}
    },
    'class_2': {
        '王五': {'age': 18, 'score': 92},
        '赵六': {'age': 17, 'score': 88}
    }
}

# 访问嵌套值
print(school['class_1']['张三']['score'])  # 95

# 修改嵌套值
school['class_2']['王五']['score'] = 95

# 添加新的嵌套数据
school['class_1']['陈七'] = {'age': 18, 'score': 91}

# 遍历嵌套字典
for class_name, students in school.items():
    print(f"\n{class_name}的学生信息：")
    for student, info in students.items():
        print(f"{student}: 年龄{info['age']}, 分数{info['score']}")
                        

class ShoppingCart:
    def __init__(self):
        self.cart = {}  # {商品名: {'price': 价格, 'quantity': 数量}}
    
    def add_item(self, name, price, quantity=1):
        if name in self.cart:
            self.cart[name]['quantity'] += quantity
        else:
            self.cart[name] = {'price': price, 'quantity': quantity}
    
    def remove_item(self, name):
        if name in self.cart:
            del self.cart[name]
    
    def update_quantity(self, name, quantity):
        if name in self.cart:
            self.cart[name]['quantity'] = quantity
    
    def get_total(self):
        return sum(item['price'] * item['quantity'] 
                  for item in self.cart.values())
    
    def view_cart(self):
        for name, info in self.cart.items():
            print(f"{name}: ¥{info['price']} x {info['quantity']} = "
                  f"¥{info['price'] * info['quantity']}")
        print(f"总计: ¥{self.get_total()}")

# 使用示例
cart = ShoppingCart()
cart.add_item("苹果", 5.0, 3)
cart.add_item("香蕉", 3.5, 2)
cart.add_item("橙子", 4.0, 4)
cart.view_cart()
                        

class GradeSystem:
    def __init__(self):
        self.grades = {}  # {学生名: {课程: 分数}}
    
    def add_grade(self, student, course, score):
        if student not in self.grades:
            self.grades[student] = {}
        self.grades[student][course] = score
    
    def get_average(self, student):
        if student in self.grades:
            scores = self.grades[student].values()
            return sum(scores) / len(scores)
        return 0
    
    def get_course_average(self, course):
        scores = [grades[course] for grades in self.grades.values() 
                 if course in grades]
        return sum(scores) / len(scores) if scores else 0
    
    def get_report(self):
        for student, courses in self.grades.items():
            print(f"\n{student}的成绩单:")
            for course, score in courses.items():
                print(f"{course}: {score}")
            print(f"平均分: {self.get_average(student):.2f}")

# 使用示例
system = GradeSystem()
system.add_grade("张三", "数学", 95)
system.add_grade("张三", "英语", 88)
system.add_grade("李四", "数学", 92)
system.add_grade("李四", "英语", 85)
system.get_report()