I have medium amateur skills in Python and I'm beginner in asm and haven't any knowledge of C-language.
I know that python C-extensions must follow specific interface to work fine.
Is this possible to write python extension in pure Assembly with the right interface and full functionality? The second question is would it be efficient enough if case of doing it right?
While googling I haven't found any examples of code or some articles or solutions about this question.
And this ISN'T the question about running asm-code from within Python so it's not duplicate of topics on SO.
In theory - it is possible.
In practice - it is highly impractical to do so. 
There are very very few cases where there is justified usage of Assembly over C, and even if you face such a situation, it is highly unlikely you will be working with Python in that case.
Also note, that the compiler can optimize the C code to extremely efficient assembly. In fact it is highly unlikely that you will hand write assembly and it will be more efficient that the compiler output, unless you are have extremely potent assembly skills, or have been writing assembly all your life..
How to write python extensions in pure asm and would it be efficient?