"**" operator in method/function interfaces ??

[Gilles Lenfant]

Hi,

What's the use of "**" in such a construct ?
<sample>
...
class MyClass:
    def __init__(self, adata, **anotherdata)
...
</sample>

I found such construct in some examples of the Tkinter tutorial at
pythonware, and in some other documents.
I have gone around all books and web language tutorial I know and did not
find anything about it.

Is there an expert here who can explain what's the use of the ** operator in
that case ?

Thanks in advance.

Gilles Lenfant