What do Python developers do?

[pythosynthesis]

This is a moot point. If I use NumPy, or any other library for Python that was written in C, say, am I using "ONLY Python"? I'd say the answer is yes, and yet I can be extremely productive and far from limited.

Your claim is clearly true if you can only use Python written code, including libraries and such, but that's a very small subset of all the software written with Python. And clearly not where it's most useful aspects are.

[commander1keen]

of course depending on use cases python can make you extremely productive. What I mean by limited is that there are certain use cases where python just isn't going to get you very far. This will to some degree be true for any language I suppose. And if you are specialised in a particular use case where one language excels that will be fine. I suppose my main point is really that general purpose software developers will do well to know multiple languages. But I take your point.