串联字典值(列表) [英] Concatenating dict values, which are lists

问题描述

假设我有以下dict对象:

Suppose I have the following dict object:

test = {}
test['tree'] = ['maple', 'evergreen']
test['flower'] = ['sunflower']
test['pets'] = ['dog', 'cat']

现在，如果我运行test['tree'] + test['flower'] + test['pets']，我会得到结果:

Now, if I run test['tree'] + test['flower'] + test['pets'], I get the result:

['maple', 'evergreen', 'sunflower', 'dog', 'cat']

这就是我想要的.

但是，假设我不确定dict对象中有哪些键，但是我知道所有值都是列表.有没有类似sum(test.values())的方法或可以运行以达到相同结果的方法?

However, suppose that I'm not sure what keys are in the dict object but I know all the values will be lists. Is there a way like sum(test.values()) or something I can run to achieve the same result?

推荐答案

您几乎给出了问题的答案: sum(test.values())只会失败，因为默认情况下它假定您要添加项目到0的起始值，当然，您不能将list添加到int.但是，如果您明确知道起始值，它将起作用:

You nearly gave the answer in the question: sum(test.values()) only fails because it assumes by default that you want to add the items to a start value of 0—and of course you can't add a list to an int. However, if you're explicit about the start value, it will work:

 sum(test.values(), [])

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