I don't necessarily know that there's anything wrong with this, but I wouldn't advise it for the sake of your career. There are a couple of problems I can think of:
- Python is hot now, but will it be in say 5-10 years? I don't know about you, but I don't desire to become the future equivalent of a COBOL mainframe programmer.
- Python won't be fast enough for every task. You can do a lot with it, but there are tasks out there that Python by itself isn't fast enough for. In these cases, you'll either need to know C (if there's one specific piece of the code that's going to run slow) or a JVM language (if you need the whole thing to be fast or are concerned with security).
I'm not OK with learning new programming languages if they don't teach me new concepts of programming and problem solving
I personally didn't see many advantages to trying Greek food until I did. Once I did try it, I was regretful that I put it off for so long. Of course, foods aren't programming languages, but the analogy actually isn't that far off. Oftentimes, the only way to see the advantages of learning a new language is to try it out.
Paul Graham called it the "Blub paradox":
Programmers get very attached to their favorite languages, and I don't want to hurt anyone's feelings, so to explain this point I'm going to use a hypothetical language called Blub. Blub falls right in the middle of the abstractness continuum. It is not the most powerful language, but it is more powerful than Cobol or machine language.
And in fact, our hypothetical Blub programmer wouldn't use either of them. Of course he wouldn't program in machine language. That's what compilers are for. And as for Cobol, he doesn't know how anyone can get anything done with it. It doesn't even have x (Blub feature of your choice).
As long as our hypothetical Blub programmer is looking down the power continuum, he knows he's looking down. Languages less powerful than Blub are obviously less powerful, because they're missing some feature he's used to. But when our hypothetical Blub programmer looks in the other direction, up the power continuum, he doesn't realize he's looking up. What he sees are merely weird languages. He probably considers them about equivalent in power to Blub, but with all this other hairy stuff thrown in as well. Blub is good enough for him, because he thinks in Blub.
When we switch to the point of view of a programmer using any of the languages higher up the power continuum, however, we find that he in turn looks down upon Blub. How can you get anything done in Blub? It doesn't even have y.
By induction, the only programmers in a position to see all the differences in power between the various languages are those who understand the most powerful one. (This is probably what Eric Raymond meant about Lisp making you a better programmer.) You can't trust the opinions of the others, because of the Blub paradox: they're satisfied with whatever language they happen to use, because it dictates the way they think about programs.
If you get the opportunity, I recommend reading the entire article.
And lastly, I can see your point in terms of wanting to specialize. But I don't think that's what you're trying to do. By definition, doing "almost any programming task" isn't what I would consider specialization. It sounds like you're using Python to generalize. If you're looking to specialize, I'd recommend going into a specific field of programming like Machine Learning or Data Warehousing or Integration. But a programming language by itself isn't much of a specialization.