That bothered me too, the default function for Ctrl-W in ipython is unix-word-rubout from python-prompt-toolkit [1], which uses spaces for word boundaries. You can rebind it to backward-kill-word so it uses "not a letter nor a digit" as a word boundary.

Here's a gist with my config (also binds shift-left/right arrow to move to previous space instead of visual select): https://gist.github.com/fratajczak/64e32421a43d3b8194d0409ce...

[1]: https://github.com/prompt-toolkit/python-prompt-toolkit/blob...