在Python中创建一个新的dict

Question

我想用Python构建一个字典。但是，我看到的所有示例都是从列表中实例化字典等。 ..

如何在Python中创建一个新的空字典？

Answer 1

使用无参数调用dict

new_dict = dict()

或简单地写

new_dict = {}

Answer 2

你可以这样做

x = {}
x['a'] = 1

Answer 3

知道如何编写预设字典也很有用：

cmap =  {'US':'USA','GB':'Great Britain'}

def cxlate(country):
    try:
        ret = cmap[country]
    except:
        ret = '?'
    return ret

present = 'US' # this one is in the dict
missing = 'RU' # this one is not

print cxlate(present) # == USA
print cxlate(missing) # == ?

# or, much more simply as suggested below:

print cmap.get(present,'?') # == USA
print cmap.get(missing,'?') # == ?

# with country codes, you might prefer to return the original on failure:

print cmap.get(present,present) # == USA
print cmap.get(missing,missing) # == RU

Answer 4

>>> dict(a=2,b=4)
{'a': 2, 'b': 4}

将在python词典中添加值。

Answer 5

d = dict()

或

d = {}

或

import types
d = types.DictType.__new__(types.DictType, (), {})

Answer 6

因此，有两种创建字典的方法：

1. my_dict = dict()

2. my_dict = {}

但是在这两个选项中，{}比dict()更有效率，而且可读性强。 CHECK HERE

Answer 7

>>> dict.fromkeys(['a','b','c'],[1,2,3])


{'a': [1, 2, 3], 'b': [1, 2, 3], 'c': [1, 2, 3]}