I don't want to knock on this accomplishment at all and I am well aware that these tools have its use-cases. However, I am just talking anecdotally and with experience with other things.
I think Google Web Toolkit started the idea of compiling X-to-Javascript. I am not sure, but it was the first I seen. I used GWT a long time ago and know it has improved a bit, but I always have sneaking feeling that the language-as-abstraction over JS feels excessive and extra work to maintain. I mean, I want to like this, but I can never justify using these toolkits. I think for something like PyQt, it really makes sense to have a language wrapper. Many people do not necessarily work in C++ or Qt's flavour of C++. But, if you are going to do anything in web dev, just learn JS/HTML/CSS. If you know that stack, these tools are really not that useful. The stack is probably the most well-documented application development space known to man now :)
However, I am always wanting to learn what people actually do and why they make tools like this. I just would never reach for this type of tool personally.
I used GWT a long time ago and it was great for being able to write a complex algorithm that had to run on the server as well as in the browser. It saved a lot of time and trouble, and you always knew that the version running on the server was the same as the one running in the browser.
If you are already adept at coding in JavaScript and you actually enjoy using JS, then you would not be the audience for these Python (or other language) web dev projects. However, if you are not a seasoned JS developer or you just don't like coding in JS as a personal preference, then I think these are worth taking a look at. I hear the phrase "just learn JavaScript" quite a bit in regards to these, but I believe learning an API is easier than learning and being proficient in an entire programming language. These tools all have their own approach as well and some are more suited to certain tasks/audiences than others.
I think Google Web Toolkit started the idea of compiling X-to-Javascript. I am not sure, but it was the first I seen. I used GWT a long time ago and know it has improved a bit, but I always have sneaking feeling that the language-as-abstraction over JS feels excessive and extra work to maintain. I mean, I want to like this, but I can never justify using these toolkits. I think for something like PyQt, it really makes sense to have a language wrapper. Many people do not necessarily work in C++ or Qt's flavour of C++. But, if you are going to do anything in web dev, just learn JS/HTML/CSS. If you know that stack, these tools are really not that useful. The stack is probably the most well-documented application development space known to man now :)
However, I am always wanting to learn what people actually do and why they make tools like this. I just would never reach for this type of tool personally.