Why Jedi not Rope

Completion comparison

So I went down to the real business: Checking for cases that might work in one library, but not in the other. So I sat down and used Spyder to compare a few things (Spyder is using Rope, but is considering to switch to Jedi). As expected I haven't found anything that is working in Rope, but not in Jedi. With Rope the following things don't complete (work in Jedi though):

• generators/iterators
• __call__ and other magic methods
• completion within classes/functions
• dynamic arrays
• *args, **kwargs
• lambdas
• simple sys.path manipulations
• invalid code, Rope cannot handle too many errors, in Jedi it will always work if some parts of the code are valid.
• performance in big files

Rope isn't "bad". It's just not as good as Jedi for autocompletion. But it's pretty clear that Rope fails to understand some basic principles of Python. For example list.append in one place will already make Rope useless.

API goodness

Jedi has a very nice and user-friendly API:

>>> import jedi
>>> source = '''import json; json.l'''
>>> script = jedi.Script(source, 1, 19, 'example.py')
>>> script
<Script: 'example.py'>
>>> completions = script.complete()
>>> completions
[<Completion: load>, <Completion: loads>]
>>> completions[0].complete
'oad'
>>> completions[0].word
'load'

So, what about Rope? The documentation says something like this:

from rope.base.project import Project
project = Project('.ropeproject')

from rope.contrib import codeassist
# Get the proposals; you might want to pass a Resource
proposals = codeassist.code_assist(project, source_code, offset)
proposals = codeassist.sorted_proposals(proposals)

proposal[0].name

While I don't know it it's possible to do the same with Rope and Jedi, it's certainly clear that there's no documentation around for Rope. It's also not clear how Rope would check for relative imports, because Rope simply doesn't know where the file it is completing is situated at (the project folder might be in an other directory).

Refactoring

This is really the place where Rope shines. I don't want to talk about this too long, but Jedi has only very limited refactoring possibilities like renaming. There's a discussion going on on github, how to improve the refactoring in Jedi. But Rope will probably always be better there.

Conclusion

Like Jedi is not really suited for refactoring, Rope is not really suited for autocompletion. In a fully fledged IDE I would recommend to use Jedi for autocompletion and Rope for refactorings. I think these two complement one another very well.

But if you are asking yourself: Which one should I choose for my editor (vim, emacs, sublime, etc)? The answer should always be Jedi. You can always add refactoring later on. But what you want in the beginning is a good and rock-solid autocompletion library.