Python - can a dict have a value that is a list?

问题:

When using Python is it possible that a dict can have a value that is a list?

for example, a dictionary that would look like the following (see KeyName3's values):

{
keyName1 : value1,
keyName2: value2,
keyName3: {val1, val2, val3}
}

I already know that I can use 'defaultdict' however single values are (understandably) returned as a list.

The reason I ask is that my code must be generic so that the caller can retieve single key values as an item (just like from a dict key-value) and not as list (without having to specify pop[0] the list) - however also retrieve multiple values as a list.

If not then any suugestions would be welcome.

If someone can help then that would be great.

Thanks in Advance,

Paul

*I'm using Python 2.6 however writing scripts that must also be forward compatible with Python 3.0+.

回答1:

Yes. The values in a dict can be any kind of python object. The keys can be any hashable object (which does not allow a list, but does allow a tuple).

You need to use [], not {} to create a list:

{ keyName1 : value1, keyName2: value2, keyName3: [val1, val2, val3] }

回答2:

Yes, it's possible:

d = {}
d["list key"] = [1,2,3]
print d

output:

{'list key': [1, 2, 3]}

回答3:

It definitely can have a list and any object as value but the dictionary cannot have a list as key because the list is mutable data structure and keys cannot be mutable else of what use are they.