用Python创建新字典

我想用Python建立字典。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？

dict无参数调用

new_dict = dict()

或简单地写

new_dict = {}

你可以这样做

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

知道如何编写预设字典对了解也很有帮助：

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

# Explicitly:
# -----------
def cxlate(country):
    try:
        ret = cmap[country]
    except KeyError:
        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

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

将值添加到python字典中。

d = dict()

要么

d = {}

要么

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

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()加上其可读性更有效。 在这里检查

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


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