这个怎么样。这里还没有提到。

Py 2和Py 3

a = {"a":2,"b":3}
a[list(a)[0]] # the first element is here
>>> 2

As others mentioned, there is no "first item", since dictionaries have no guaranteed order (they're implemented as hash tables). If you want, for example, the value corresponding to the smallest key, thedict[min(thedict)] will do that. If you care about the order in which the keys were inserted, i.e., by "first" you mean "inserted earliest", then in Python 3.1 you can use collections.OrderedDict, which is also in the forthcoming Python 2.7; for older versions of Python, download, install, and use the ordered dict backport (2.4 and later) which you can find here.

Python 3.7 现在字典是按插入顺序排列的。

如果你只需要访问一个元素(碰巧是第一个元素，因为字典不保证顺序)，你可以在Python 2中简单地这样做:

my_dict.keys()[0]    # key of "first" element
my_dict.values()[0]  # value of "first" element
my_dict.items()[0]   # (key, value) tuple of "first" element

请注意(据我所知)Python不能保证连续两次调用这些方法中的任何一个都会返回相同顺序的list。Python3不支持这一点。

在Python 3中:

list(my_dict.keys())[0]    # key of "first" element
list(my_dict.values())[0]  # value of "first" element
list(my_dict.items())[0]   # (key, value) tuple of "first" element

没有外部库，适用于Python 2.7和3.x:

>>> list(set({"a":1, "b": 2}.values()))[0]
1

对于任意键，省略.values()

>>> list(set({"a":1, "b": 2}))[0]
'a'

子类化字典是一种方法，但效率不高。这里如果你提供一个整数，它将返回d[list(d)[n]]，否则按预期访问字典:

class mydict(dict):
    def __getitem__(self, value):
        if isinstance(value, int):
            return self.get(list(self)[value])
        else:
            return self.get(value)

d = mydict({'a': 'hello', 'b': 'this', 'c': 'is', 'd': 'a',
            'e': 'test', 'f': 'dictionary', 'g': 'testing'})

d[0]    # 'hello'
d[1]    # 'this'
d['c']  # 'is'

在python3中，方法是:

dict.keys() 

返回一个类型为:dict_keys()的值，当获取dict的key的第一个成员时，我们将得到一个错误:

dict.keys()[0]
TypeError: 'dict_keys' object does not support indexing

最后，我将dict.keys()转换为list @1st，并通过列表拼接方法获得了第一个成员:

list(dict.keys())[0]