From http://stackoverflow.com/questions/26321333/tkinter-in-python-3-4-on-windows-dont-post-internal-clipboard-data-to-the-windo

I use the following code to place result in clipboard.

from tkinter import Tk
r = Tk()
r.withdraw()
r.clipboard_clear()
r.clipboard_append("Result")

It works fine on Python version 3.3.5 and earlier. But in Python 3.4 it was receive empty clipboard. If I prevent the script from the immediate exit, adding input() after clipboard_append(), I see that clipboard contains the correct "Result".

If I run script, switch to any other window and press Ctrl+V, I receive "Result" and "Result" remains in clipboard after script exits.

I think in tcl/tk 8.6 clipboard_clear() affect system clipboard, but clipboard_append affect only internal tcl/tk clipboard that transfered to system clipboard only by OS request. Looks like it was done in Linux, that don't have system clipboard.

I don't believe there's anything Python can do about this, unless it can be confirmed that this is a bug that's been fixed in a more recent version of Tcl/Tk 8.6, in which case we can update our dependency.  The easy test for whether updating Tcl/Tk in 3.4 (which uses 8.6.1) will do any good is to try this out with 3.5.0b2 (which uses the latest 8.6.4).

Here is minimal reproducer on Tcl/Tk. I don't have a workaround.

I tested the code posted by Victor with Python 3.5 (which uses Tcl/Tk 8.6.4) and I still get an empty clipboard when the script exits.

I also downloaded ActiveState's Tcl binary which is also version 8.6.4, and tested the minimal reproducer posted by Serhiy with this

    wish issue23760.tcl

and it works i.e. I get "Result" in the system clipboard.

I don't really know what to make of this.

Related Tk issues:

http://core.tcl.tk/tk/tktview/822002ffffffffffffff
http://core.tcl.tk/tk/tktview/732662ffffffffffffff
http://core.tcl.tk/tk/tktview/1844034fffffffffffff
http://core.tcl.tk/tk/tktview/939389ffffffffffffff

The problem should be fixed (at least on Windows) in the last issue, but perhaps Tkinter doesn't execute this code.

A workaround is to make a pause about 0.1 sec (can be depend on perfomance of your computer, it doesn't work if the pause is too short). Append following lines to you example:

r.after(100, r.destroy)
r.mainloop()