I am currently developing a cross platform GUI application with Python, and tkinter.  
Although I'm German, I want all button labels to be displayed in English. By now it is a strange mix because the messages in tkMessageBoxes are in English but button labels and file dialog boxes are in German.  
Is there a way to force Python / tkinter to use English labels only?
On both Linux and Windows, Tcl will use the value of the LANG environment variable if set to initialize the locale. So if you set LANG=en you will get an English locale. If this is not set, then on Windows it then examines the registry to identify the locale in use and configures from that. You can find the Tcl code doing this in the msgcat.tcl file (search for registry).
It will use LC_ALL, LC_MESSAGES or LANG in that order from the environment.
Forcing tkinter to 'speak' English