What does it mean that certain datatypes cannot be keys?

Frequently Asked Questions Python FAQ
1

We can have a list or a dictionary as a value of an item in a dictionary, but we cannot use these data types as keys of the dictionary. If we try to, we will get a TypeError . i really dont understand these lines

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2

dictionaries consist of key value pairs:

d = {
   'key': 'value'
}

what these lines are saying is that the value of a dictionary can be a dictionary or a list:

d = {
   'my_list': ['item1', 'item2', 'item3'],
   'my_dict': {'key': 'value'}
}

the keys (my_list, my_dict and key) are strings. So that is valid. The moment you attempt to use a list or dictionary as key for a dictionary, you will get a type error.

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3

A post was split to a new topic: S there any specific reason why to use a list as a key

4

Keys must be unique all time and whatever happens. Lists and dictionaries can be changed.

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