Maybe there are two special cases colliding here:

1. complete("A.foo", 0) returns "A.foo(". But the opening bracket is in readline.get_completer_delims(), which means the completer has suggested not only a “word” but also a delimiter.

2. Perhaps Lorenz has taken "A.foo(" directly and passed it back to the completer. But as Robert said, if Readline were used, it would see the bracket as a delimiter, and only pass an empty string as the text.

The question is how should the completer behave when it gets (invalid) input that would not be possible from default Readline usage?

Lorenz: why are you passing "A.foo(" to the completer, when it only parses attribute names, and not other Python syntax such as brackets?