[brythonfailing]

Not that I have anything against Brython (which imo is a cool project, although I'm not so sure if it's practical yet), but since you asked for it, here's an example where it does differ from python:

  x = 0
  
  def impure():
      global x
      x += 1
      return x

  print(0 < impure() <= 1)

In python, impure() would only be evaluated once returning True, but Brython's chaining evaluates it twice, and so it returns False instead. Of course, this example isn't exactly something you'd usually see in actual code (heck, it's probably even bad practice in most situations) BUT the point here is that while most of python might be compatible with this, there exists some inconsistencies that causes one's previously working python code to fail (and these bugs would probably be very difficult to trace). Of course, Brython is still young and has time to hopefully fix these issues. (In fact, this is the second time I've tried this project. Back then they didn't even have the chaining feature working, so it's nice that they are making progress.)

[richo]

Nifty example, but this is why we have integration test suites.

PyPy, jython, ironpython etc all had/have incompatibilities as the language evolves and as they work out the quirks in their respective runtimes.

This isn't compatible with cpython (afaik, none of the other runtimes have ever been COMPLETELY compatible, but this is much further off), but hell, it's pretty awesome.

As an aside, I'd shoot anyone who did that ^^ without a pretty amazing explaination.

[stuaxo]

Well... if brython is running the CPython integration tests to aim for proper compatibility then fair enough.

It is a cool project, whichever one of these python in javasript things is to become successful needs to aim for the same level of compatibility as say Jython or IronPython - yes it would take a long time, but this sort of thing is needed to be a useful implementation.