# 创建一个字典
my_dict = {'name': 'John', 'age': 25, 'city': 'New York'}# 访问字典中的值
print(my_dict['name'])  # 输出: John# 添加新的键值对
my_dict['gender'] = 'Male'# 更新字典中的值
my_dict['age'] = 26# 删除键值对
del my_dict['city']# 检查键是否存在
if 'name' in my_dict:print('Name is present in the dictionary.')# 遍历字典
for key, value in my_dict.items():print(f'{key}: {value}')