I would suggest taking a look at wxPython which is a set of python bindings for the wxWidgets GUI toolkit.
This provides a native look and feel on all of Windows, OS-X & Linux and can be used to produce very professional looking a GUI from python.
To get an introduction to wxPython for Python 2.7 download and install it plus the documents & demo suite.
Python 3 support is an in progress project called Project Phoenix that, while it is not yet at the first official release, works well to provide a very good, cross platform, GUI for most projects. Installation of the latest build can be done with the line:
pip install --upgrade --trusted-host wxpython.org --pre -f http://wxpython.org/Phoenix/snapshot-builds/ wxPython_Phoenix
but installation of the documents and demos package requires downloading the source from github.
- Free, Gratis & Open Source
- Licence permits commercial use as well as personal & academic
- Cross Platform Windows, OS-X & Windows
- Native Look & Feel utilises native components where ever possible
- Large & Active user & developer communities
- Mature - wxPython initial release was in 1998!
- A lot of online help & books available
- Numerous Applications already using wxPython
Example Apps
PySpread Pythonic Spreadsheet
Cornice Cross Platform Image Browser
OpenDict Open Source multiplatform computer dictionary.

All screenshots from the respective programs web site.
argparse
to parse your command line arguments, there are a few apps which will scan your code, look for availabel arguments and generate a GUI.