You need to either specify the path as the first positional argument, or use the keyword argument "bitmap". It's rather poorly documented, but the bitmap argument is required; you can't just give the default keyword argument. In fact, the bitmap keyword argument has been removed in python 3.

However, you can only use .ico files on windows. On ubuntu and other linux boxes you need to use a .xbm file, and need to prefix it with "@"

This should work on windows only:

gui.iconbitmap('/home/me/PycharmProjects/program/icon.ico')
On ubuntu, it would need to be something like this:

gui.iconbitmap('@/home/me/PyCharmProjets/program/icon.xbm')
You can't just rename a .ico file to .xbm, they are completely different file formats.

This is the Tkinter introduction, last updated in November 2005. This is a work in progress.