There are three pieces of user-specified configuration: (1) the number of spaces for a tab set in IDLE's config, (2) the sys.ps1 value, and (3) the sys.ps2 value.

Currently IDLE's shell is ignoring (1) while the editor is not. IDLE's shell is ignoring (3) while the python shell isn't. I think the obvious solution is to make IDLE's shell follow the same behavior as IDLE's editor and the python shell.

The draw back comes from variable-pitch fonts, but I think using variable-pitch fonts is a minority use case and will create spacing issues regardless (compared pasting 8 spaces and pasting 1 tab into the editor with Lucida Sans Unicode). Special cases aren't special enough to break the rules.

This issue is concerned with mixed tabs and spaces in the IDLE shell, which has a simple fix. Putting the >>> and ... prompts in a separate space so that they are not copied can be done in a separate issue.