The file extension 'pythonguifile' is not a recognized or standardized file format used across the industry. It is highly probable that this extension is a custom designation used by a specific, proprietary Python application or a personal development project. Files bearing this extension are typically used to save configuration settings, project layouts, or the current state of a Graphical User Interface (GUI) application built using Python frameworks such as Tkinter, PyQt, Kivy, or wxPython. The internal structure of the file—which could range from simple plain text, JSON, or XML, to a serialized Python object (using the 'pickle' module)—is entirely dependent on the specific developer or application that generated it. Consequently, these files are generally not intended for general distribution or use outside of the specific software environment that created them. To successfully open, modify, or interpret the contents of a .pythonguifile, one would require access to the original Python application or its source code.