Python中dict支持多个key的方法新家

# 创建一个字典，使用元组作为键
multi_key_dict = {
    (1, 'a'): 'value1',
    (2, 'b'): 'value2',
    (3, 'c'): 'value3'
}
 
# 检索值
key = (2, 'b')
value = multi_key_dict.get(key)
print(f"The value for key {key} is {value}")
 
# 插入新值
multi_key_dict[(4, 'd')] = 'value4'
print(multi_key_dict)
 
# 更新值
multi_key_dict[(1, 'a')] = 'new_value1'
print(multi_key_dict)

The value for key (2, 'b') is value2
{(1, 'a'): 'new_value1', (2, 'b'): 'value2', (3, 'c'): 'value3', (4, 'd'): 'value4'}
{(1, 'a'): 'new_value1', (2, 'b'): 'value2', (3, 'c'): 'value3', (4, 'd'): 'value4'}

# 创建一个嵌套字典
nested_dict = {
    1: {'a': 'value1_a', 'b': 'value1_b'},
    2: {'a': 'value2_a', 'c': 'value2_c'},
    3: {'b': 'value3_b', 'c': 'value3_c'}
}
 
# 检索值
primary_key = 2
secondary_key = 'a'
value = nested_dict.get(primary_key, {}).get(secondary_key)
print(f"The value for keys {primary_key} and {secondary_key} is {value}")
 
# 插入新值
primary_key_new = 4
secondary_key_new = 'd'
value_new = 'value4_d'
if primary_key_new not in nested_dict:
    nested_dict[primary_key_new] = {}
nested_dict[primary_key_new][secondary_key_new] = value_new
print(nested_dict)
 
# 更新值
nested_dict[1]['a'] = 'new_value1_a'
print(nested_dict)

The value for keys 2 and a is value2_a
{1: {'a': 'new_value1_a', 'b': 'value1_b'}, 2: {'a': 'value2_a', 'c': 'value2_c'}, 3: {'b': 'value3_b', 'c': 'value3_c'}, 4: {'d': 'value4_d'}}
{1: {'a': 'new_value1_a', 'b': 'value1_b'}, 2: {'a': 'value2_a', 'c': 'value2_c'}, 3: {'b': 'value3_b', 'c': 'value3_c'}, 4: {'d': 'value4_d'}}

from collections import defaultdict
 
# 创建一个嵌套defaultdict
nested_defaultdict = defaultdict(lambda: defaultdict(str))
 
# 插入值
nested_defaultdict[1]['a'] = 'value1_a'
nested_defaultdict[2]['b'] = 'value2_b'
nested_defaultdict[3]['c']['d'] = 'value3_c_d'  # 注意这里我们创建了一个更深层次的嵌套
 
# 检索值
primary_key = 2
secondary_key = 'b'
value = nested_defaultdict[primary_key][secondary_key]
print(f"The value for keys {primary_key} and {secondary_key} is {value}")
 
# 更新值
nested_defaultdict[1]['a'] = 'new_value1_a'
print(nested_defaultdict)

The value for keys 2 and b is value2_b
defaultdict(<function <lambda> at 0x...>, {1: defaultdict(str, {'a': 'new_value1_a'}), 2: defaultdict(str, {'b': 'value2_b'}), 3: defaultdict(str, {'c': defaultdict(str, {'d': 'value3_c_d'})})})

my_dict = {
    1: 'integer key',
    -3.14: 'float key',  # 注意：一般不推荐使用浮点数作为键
    'string': 'string key',
    (1, 2, 3): 'tuple key',
    True: 'boolean key',
    None: 'none key',
    frozenset([4, 5]): 'frozenset key'
}
 
# 访问字典中的值
print(my_dict[1])         # 输出: integer key
print(my_dict[(1, 2, 3)]) # 输出: tuple key
print(my_dict[True])      # 输出: boolean key
 
# 尝试使用不支持的数据类型作为键（会导致错误）
# my_dict = {[1, 2]: 'list key'}  # TypeError: unhashable type: 'list'