It isn't. Frankly, it isn't even top 3 in any "field of computing" depending on how you define "field of computing".
What python has going for it is the evangelists who do a great job of spreading the word and of course funding - they have lots of money backing the language. Also, being an interpreted language, it has a much lower barrier to entry.
I'm not much of a fan of python and its block syntax - I very much prefer braces or markers delineating the beginning and end of code blocks.
Also, python wants to be everything ( functional, OO, imperative, etc ) and hence is the worst language to learn programming language topics in my humble opinion.
My hope is that python will serve as a "gateway drug" to other languages like ruby, ML, C/C++, SQL, etc. So that people will learn what programming and languages are rather using python as a glorified calculator which I'm sure many are doing.