Common ways to create dictionaries in python

python字典以“鍵-值對”形式存在,所有的元素放在一對大括號“{}”中;
字典中的“鍵”是不允許重復,“值”是可以重復的.
以下總結了3A dictionary construction method

一、直接賦值法
使用=將一個字典賦值給一個變量,That is, you can create a dictionary variable.

# # 直接賦值
a = {
}
b = {
'a': 1, 2: 'a', 1: 2, "b": 1, '''c''': 1}
print('空字典：', a, type(a))
print('字典b：', b, type(b))

空字典：{} <class ‘dict’>
字典b ：{‘a’: 1, 2: ‘a’, 1: 2, ‘b’: 1, ‘c’: 1}<class ‘dict’>
注：Use single quotes in dictionaries、雙引號、三引號都可以,這點跟jsonThe format data is different,jsonFormat data can only use double quotes.

二、內置函數dict()
使用內置函數dict快速創建字典
**用法1：**創建空字典

# 內置函數dict()
a = dict()
print(a, type(a))

結果：{} <class ‘dict’>

**用法2：**將2A list format data is combined into a dictionary

# 將2A list of data is combined into a dictionary
keys = ['a', 'b', 'c']
values = [1, 2, 3]
dict1 = dict(zip(keys, values))
print('結果：', dict1)

結果：{‘a’: 1, ‘b’: 2, ‘c’: 3}
注：When combining dictionaries using this method,要保證2lists are the same length.

**用法3：**根據給定的“鍵-值對”創建字典

# Creates a dictionary from the given key-value pairs
dict1 = dict(a=1, b=2, c=3, d='a')
print('結果：', dict1)

結果：{‘a’: 1, ‘b’: 2, ‘c’: 3, ‘d’: ‘a’}

**用法4：**The given content is“鍵”,創建“值”為空的字典

# # The given content is the key,Creates a list with an empty value
dict1 = dict.fromkeys(['a', 'b', 'c'])
dict2 = dict.fromkeys({
'a', 'b', 'c'})
dict3 = dict.fromkeys(('a', 'b', 'c'))
print('結果1：', dict1)
print('結果2：', dict2)
print('結果3：', dict3)

結果1：{‘a’: None, ‘b’: None, ‘c’: None}
結果2：{‘c’: None, ‘b’: None, ‘a’: None}
結果3：{‘a’: None, ‘b’: None, ‘c’: None}
注：dict.fromkeys()The value type inside can be a list、集合、元組.

**用法5：**創建所有“鍵”對應的“值”相同的字典

# Create a dictionary with all keys corresponding to the same value
dict1 = dict.fromkeys(['a', 'b', 'c'], 1)
dict2 = dict.fromkeys(['a', 'b', 'c'], [1,2])
print('值全為1的字典：', dict1)
print('值全為[1,2]的字典：', dict2)

值全為1的字典：{‘a’: 1, ‘b’: 1, ‘c’: 1}
值全為[1,2]的字典：{‘a’: [1, 2], ‘b’: [1, 2], ‘c’: [1, 2]}

三、字典推導式
Create a dictionary using dictionary comprehensions

# Create a dictionary using dictionary comprehensions
dict1 = {
key:values for (key, values) in []}
dict2 = {
key: values for (key, values) in zip(['a', 'b', 'c'], [1, 2, 'a'])}
print('結果1：', dict1)
print('結果2：', dict2)

結果1：{}
結果2：{‘a’: 1, ‘b’: 2, ‘c’: ‘a’}

以上就是構建python字典的常見用法,Different usages can be selected according to actual needs.

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