如何向python中的字典键添加多个值？
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How to add multiple values to a dictionary key in python?
提问by PythonEnthusiast
I want to add multiple values to a specific key in a python dictionary. How can I do that?
我想向 python 字典中的特定键添加多个值。我怎样才能做到这一点？
a = {}
a["abc"] = 1
a["abc"] = 2
This will replace the value of a["abc"] from 1 to 2.
这会将 a["abc"] 的值从 1 替换为 2。
What I want instead is for a["abc"] to have multiple values(both 1 and 2).
我想要的是 a["abc"] 具有多个值（1 和 2）。
回答by MattDMo
How about
怎么样
a["abc"] = [1, 2]
This will result in:
这将导致：
>>> a
{'abc': [1, 2]}
Is that what you were looking for?
这就是你要找的吗？
回答by President James K. Polk
Make the value a list, e.g.
将值设为列表，例如
a["abc"] = [1, 2, "bob"]
UPDATE:
更新：
There are a couple of ways to add values to key, and to create a list if one isn't already there. I'll show one such method in little steps.
有几种方法可以向键添加值，并在没有列表的情况下创建一个列表。我将逐步展示一种这样的方法。
key = "somekey"
a.setdefault(key, [])
a[key].append(1)
Results:
结果：
>>> a
{'somekey': [1]}
Next, try:
接下来，尝试：
key = "somekey"
a.setdefault(key, [])
a[key].append(2)
Results:
结果：
>>> a
{'somekey': [1, 2]}
The magic of setdefaultis that it initializes the value for that key ifthat key is not defined, otherwise it does nothing. Now, noting that setdefaultreturns the key you can combine these into a single line:
的神奇之处setdefault在于，如果该键未定义，它会初始化该键的值，否则它什么都不做。现在，注意setdefault返回键，您可以将它们组合成一行：
a.setdefault("somekey",[]).append("bob")
Results:
结果：
>>> a
{'somekey': [1, 2, 'bob']}
You should look at the dictmethods, in particular the get()method, and do some experiments to get comfortable with this.
你应该看看dict方法，特别是get()方法，并做一些实验来适应这一点。
