students = {'Alice': 18, 'Bob': 20, 'Charlie': 21}

# 使用方括号访问map中的元素
print(students['Alice'])  # 输出: 18

# 使用get()方法获取元素的值
print(students.get('Bob'))  # 输出: 20

students['Charlie'] = 22  # 修改值
students['David'] = 19  # 创建新的键值对

print(students)  # 输出: {'Alice': 18, 'Bob': 20, 'Charlie': 22, 'David': 19}

for key, value in students.items():
    print(key, value)

del students['Charlie']  # 删除键为'Charlie'的元素

print(students)  # 输出: {'Alice': 18, 'Bob': 20, 'David': 19}

fruit_colors = {'apple': 'red', 'banana': 'yellow', 'orange': 'orange'}

print(fruit_colors['apple'])  # 输出: red
print(fruit_colors.get('banana'))  # 输出: yellow

fruit_colors['orange'] = 'green'  # 修改值
fruit_colors['grape'] = 'purple'  # 创建新的键值对

print(fruit_colors)  # 输出: {'apple': 'red', 'banana': 'yellow', 'orange': 'green', 'grape': 'purple'}

for key, value in fruit_colors.items():
    print(key, value)

del fruit_colors['banana']

print(fruit_colors)  # 输出: {'apple': 'red', 'orange': 'green', 'grape': 'purple'}