python怎么获取字典所有的键或值_python获取字典键值对方法

.keys()

.values()

.items()

.keys()

dict_keys

my_dict = {
    "name": "Alice",
    "age": 30,
    "city": "New York",
    "occupation": "Engineer"
}

all_keys = my_dict.keys()
print(f"获取到的所有键 (dict_keys 对象): {all_keys}")

# 遍历键
print("\n遍历所有键:")
for key in all_keys:
    print(key)

# 转换为列表 (如果需要一个列表副本)
keys_list = list(all_keys)
print(f"\n转换为列表后的键: {keys_list}")

# 转换为集合 (如果需要去重或进行集合操作)
keys_set = set(all_keys)
print(f"转换为集合后的键: {keys_set}")

.values()

dict_values

my_dict = {
    "name": "Alice",
    "age": 30,
    "city": "New York",
    "occupation": "Engineer"
}

all_values = my_dict.values()
print(f"获取到的所有值 (dict_values 对象): {all_values}")

# 遍历值
print("\n遍历所有值:")
for value in all_values:
    print(value)

# 转换为列表
values_list = list(all_values)
print(f"\n转换为列表后的值: {values_list}")

# 转换为集合 (这在值可能重复时很有用，可以快速获取不重复的值)
values_set = set(all_values)
print(f"转换为集合后的值: {values_set}")

.items()

dict_items

(key, value)

my_dict = {
    "name": "Alice",
    "age": 30,
    "city": "New York",
    "occupation": "Engineer"
}

all_items = my_dict.items()
print(f"获取到的所有键值对 (dict_items 对象): {all_items}")

# 遍历键值对
print("\n遍历所有键值对:")
for key, value in all_items:
    print(f"键: {key}, 值: {value}")

# 转换为列表 (每个元素是一个元组)
items_list = list(all_items)
print(f"\n转换为列表后的键值对: {items_list}")

.keys()

.values()

.items()

for

my_dict = {"a": 1, "b": 2, "c": 3}
for key in my_dict.keys():
    print(f"处理键: {key}")

for key in list(my_dict.keys()):

my_dict.values()

my_dict.items()

list()

list

set

dict_keys

dict_values

dict_items

my_dict.keys()

my_dict

all_keys

my_dict = {"name": "Alice", "age": 30}
all_keys = my_dict.keys()
print(f"初始键视图: {all_keys}") # dict_keys(['name', 'age'])

my_dict["city"] = "London" # 添加一个新键
print(f"添加键后的视图: {all_keys}") # dict_keys(['name', 'age', 'city'])

del my_dict["age"] # 删除一个键
print(f"删除键后的视图: {all_keys}") # dict_keys(['name', 'city'])

dict_keys

dict_keys

|

&

-

^

dict_a = {"apple": 1, "banana": 2, "cherry": 3}
dict_b = {"banana": 4, "date": 5}

# 交集：两个字典都有的键
common_keys = dict_a.keys() & dict_b.keys()
print(f"共有键: {common_keys}") # {'banana'}

# 并集：所有不同的键
all_unique_keys = dict_a.keys() | dict_b.keys()
print(f"所有不同键: {all_unique_keys}") # {'apple', 'banana', 'cherry', 'date'}

# 差集：dict_a有但dict_b没有的键
keys_in_a_only = dict_a.keys() - dict_b.keys()
print(f"dict_a独有键: {keys_in_a_only}") # {'apple', 'cherry'}

dict_values

dict_items

set

dict_keys

dict_values

dict_items

RuntimeError: dictionary changed size during iteration

my_dict = {"a": 1, "b": 2, "c": 3}
# 错误示例：在迭代时修改字典结构
# try:
#     for key in my_dict.keys():
#         if key == "b":
#             del my_dict["c"] # 尝试删除一个键
#         print(key)
# except RuntimeError as e:
#     print(f"捕获到运行时错误: {e}")

# 正确处理方式：先转换为列表进行迭代
keys_to_process = list(my_dict.keys())
for key in keys_to_process:
    if key == "b":
        my_dict["d"] = 4 # 可以安全地添加新键，因为它不会影响当前迭代的列表
        print(f"添加了键 'd'")
    print(f"处理键: {key}")
print(f"最终字典: {my_dict}")