20 个 Python 字典映射技巧，让数据处理更高效

# 使用zip函数结合列表，一键成字典
keys = ['name', 'age']
values = ['Alice', 24]
my_dict = dict(zip(keys, values))
print(my_dict)
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numbers = [1, 2, 3, 4]
squares = {num: num*num for num in numbers}
print(squares)
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my_dict = {'name': 'Bob'}
print(my_dict.get('age', 'Not Found'))  # 不怕找不到，直接告诉你“Not Found”
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# pop方法，删除并返回值
age = my_dict.pop('age', 'Already gone')  # 如果不存在，就默认返回'Already gone'
print(age)
print(my_dict)  # 看，'age'没了
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dict1 = {'a': 1, 'b': 2}
dict2 = {'b': 3, 'c': 4}
dict1.update(dict2)
print(dict1)  # 'b'的值被更新，'c'加入，合并就这么简单
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for key, value in my_dict.items():
    print(f"Key: {key}, Value: {value}")
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keys_only = my_dict.keys()
values_only = my_dict.values()
print(list(keys_only))  # 转成列表方便查看
print(list(values_only))
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if 'age' in my_dict:
    print("Age is there!")
else:
    print("Sorry, no age.")
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print(len(my_dict))  # 瞬间知道字典大小
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# 按值排序
sorted_dict = sorted(my_dict.items(), key=lambda x: x[1])
print(sorted_dict)

# 按键排序
sorted_by_key = sorted(my_dict.items())
print(sorted_by_key)
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list_of_tuples = list(my_dict.items())
print(list_of_tuples)
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my_dict.clear()
print(my_dict)  # 空空如也，准备迎接新的数据
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nested_dict = {
    'person1': {'name': 'Alice', 'age': 24},
    'person2': {'name': 'Bob', 'age': 30}
}
print(nested_dict['person1']['name'])  # 访问内层，深挖数据
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keys_list = ['name', 'age', 'city']
default_values = None
my_init_dict = dict.fromkeys(keys_list, default_values)
print(my_init_dict)  # 统一初始值，批量创建
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dict_a = {'x': 1, 'y': 2}
dict_b = {'y': 3, 'z': 4}
{**dict_a, **dict_b}  # **操作符，解包合并，新字典诞生
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from collections import defaultdict

# 创建一个默认值为列表的字典
my_default_dict = defaultdict(list)
my_default_dict['fruits'].append('apple')
my_default_dict['fruits'].append('banana')
print(my_default_dict)
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import copy

original_dict = {'a': [1, 2], 'b': 3}
shallow_copy = copy.copy(original_dict)
deep_copy = copy.deepcopy(original_dict)

# 修改原字典中的列表
original_dict['a'][0] = 99

print("Original:", original_dict)
print("Shallow Copy:", shallow_copy)  # 浅拷贝受影响
print("Deep Copy:", deep_copy)  # 深拷贝不受影响
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my_dict = {'name': 'Alice', 'age': 24}
keys_view = my_dict.keys()
print("Initial Keys:", keys_view)

# 添加新的键值对
my_dict['city'] = 'Wonderland'
print("Keys after update:", keys_view)  # 视图自动更新
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data = [('John', 'Doe', 23), ('Jane', 'Doe', 24)]
people = {f"{first} {last}": age for first, last, age in data}
print(people)
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my_dict = {}
my_dict.setdefault('score', []).append(90)
my_dict.setdefault('score', []).append(95)
print(my_dict)  # 避免了多次检查和初始化
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