What does None mean here?

[jenniferruurs]

What does None mean here?
Does it mean that it should be initialized as empty, but if there is input it can be overridden?

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class ListNode:           def __init__(self, data=None, next=None):         self.data = data         self.next = next

[buran]

None is default value of data and next. If you don't pass any of these during instantiation of the class object it will use the default values.

as a side note next is built-in function, better don't use it as param name