He creates a list interpreted as queue which already contains the root node. The queue needs a first element otherwise the while loop would not execute its body.

It's a list with node as its first element. Actually that , doesn't need to be there as it's a list. I guess I wanted to use a tuple instead of a list. In case of tuple the , is necessary:

>>> (2) == 2  
True
>>> type((2))
<class 'int'>
>>> type((2,))
<class 'tuple'>
>>> (2,)[0] == 2

Regards,

suic

It is a list with one element "node".