如何在变量中提取词典单键值对 [英] How to extract dictionary single key-value pair in variables

问题描述

我在字典中只有一个键值对。我想要将键分配给一个变量
，它的值是另一个变量。我尝试过以下方法，但是我收到相同的错误。

I have only a single key-value pair in dictionary. I want to assign key to one variable and it's value to another variable. I have tried with below ways but I am getting error for same.

>>> d ={"a":1}

>>> d.items()
[('a', 1)]

>>> (k,v) = d.items()
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: need more than 1 value to unpack

>>> (k, v) = list(d.items())
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
ValueError: need more than 1 value to unpack

我知道我们可以提取密钥和值，或者通过for循环和iteritems（），但是不是有一个简单的方法，以便我们可以在单个语句中分配？

I know that we can extract key and value one by one, or by for loop and iteritems(), but isn't there a simple way such that we can assign both in single statement?

推荐答案

添加另一个级别，使用元组（只是逗号）：

Add another level, with a tuple (just the comma):

(k, v), = d.items()

或列表：

[(k, v)] = d.items()

或选择第一个元素：

k, v = d.items()[0]

前两个如果您的字典有多个键，则它们会引发异常，并且都可以在Python 3上工作，而后者必须拼写为 k，v = next（iter（d.items（ ）））工作。

The first two have the added advantage that they throw an exception if your dictionary has more than one key, and both work on Python 3 while the latter would have to be spelled as k, v = next(iter(d.items())) to work.

演示：

>>> d = {'foo': 'bar'}
>>> (k, v), = d.items()
>>> k, v
('foo', 'bar')
>>> [(k, v)] = d.items()
>>> k, v
('foo', 'bar')
>>> k, v = d.items()[0]
>>> k, v
('foo', 'bar')
>>> k, v = next(iter(d.items()))  # Python 2 & 3 compatible
>>> k, v
('foo', 'bar')

这篇关于如何在变量中提取词典单键值对的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！