如何更改字典的键和值

my_dict = {'a': 1, 'b': 2, 'c': 3}
my_dict['a'] = 'A'  # 更改键'a'的值为'A'
my_dict['d'] = 4   # 添加新的键值对'd': 4
print(my_dict)     # 输出：{'a': 'A', 'b': 2, 'c': 3, 'd': 4}

my_dict = {'a': 1, 'b': 2, 'c': 3}
updated_dict = {k.upper(): v*2 for k, v in my_dict.items()}  # 将键转为大写，值乘以2
print(updated_dict)  # 输出：{'A': 2, 'B': 4, 'C': 6}

my_dict = {'a': 1, 'b': 2, 'c': 3}
value = my_dict.pop('a')   # 删除键'a'并获取其对应的值
my_dict.setdefault('A', value)  # 添加新的键值对'A': 1
print(my_dict)  # 输出：{'A': 1, 'b': 2, 'c': 3}