Nah, I would love people to use Python -- just to help improve it as well (either through libraries, alternative languages or submitting changes through official channels.)
Saying I am "self aggrandising" is disingenuous and misleading at best.
... Yeah, that's gnarly. :D
That is emulating `let` using lambdas, though, and not mutable assignment. Still useful if you really want to nest them, but still immutable.
Mutation in lambdas is not compatible with your complaint about "inadequate support for high-level functional programming", as it goes against the principles of FP.
You can't do that in Haskell either, and any FP purist would blanch at a statement like that.
That seems like an exceedingly error-prone thing to write. "x +=1" isn't a value and the unmanaged mutation will be surprising when it happens. On a Python implementation with parallelism (e.g. Jython) you could very easily end up losing updates - on CPython the GIL will probably mean your code accidentally doesn't exhibit that problem, but that doesn't seem a very desirable way to code.
Something like functional reactive programming style, where you explicitly define a pipeline from foo.click to x and explicitly gather together all your pipelines (explicitly defining the interleaving semantics rather than just "whenever an event happens it happens") and run them in one place.