When typing the ' key or the " key on the IDLE Python application for macOS, the application. I think it might have something to do with that beta version of Tcl/Tk (8.5.9) as Python says it is 'unstable'.
Yes, this is a symptom of using the default Apple-supplied macOS Tcl/Tk. See https://www.python.org/download/mac/tcltk/ for more information as the warning in IDLE suggests. If you are using Python 3.6.0 downloaded from python.org, the simple solution is to install the latest Tcl/Tk 8.5.x (not 8.6.x) from ActiveState assuming your use is compatible with the ActiveTcl license.
Marco, did you see this message? (r"WARNING: The version of Tcl/Tk ({0}) in use may" r" be unstable.\n" r"Visit http://www.python.org/download/mac/tcltk/" r" for current information.".format(patchlevel)) Or is it somehow lost? Ned, the version check for this message is only done for Cocoa. Is this restriction correct?