Simple Is Good

The PySimpleGUI project has two main goals: a simpler method for creating graphical user interfaces (GUIs), and common code for Tkinter, QT, Wx, and web graphics. Although I feel comfortable doing my own Python Tkinter and web interfaces, having common code for both local GUI and web apps could be extremely useful, especially for Raspberry Pi projects. In this article, I introduce PySimpleGUI and create both a local GUI and a web interface to control a Raspberry Pi rover, all in less than 60 lines of code.

Getting Started

The Python PySimpleGUI [1] project has a number of "ports" or versions. The main full-featured version is for Tkinter-based graphics. The versions for Qt, Wx, and web graphics are still in development, so some testing will be required if you are hoping for full code compatibility between the different libraries.

Although you probably won't encounter a lot of cases in which you would want to flip between Qt, Wx, and Tkinter graphic engines, the possibility exists. Figure 1 shows examples of the same code applied to the different graphic libraries.

Figure 1: PySimpleGUI uses the graphic libraries for (top to bottom) Tkinter, Qt, Wx, and a web app.

To install the default version of PySimpleGUI for Tkinter enter:

pip install pysimpleGUI

PySimpleGUI has a wide range of graphic widgets or elements. Graphic presentations are built by creating a layout variable, and elements are placed in separate rows defined by enclosing square brackets. A row can have a single element or multiple elements. Figure 2 is a graphic GUI example with three rows.

Figure 2: PySimpleGUI layout example.

A Button Interface

The rover project I create in this article uses a five-row layout (Listing 1; Figure 3). The first row contains feedback text, and rows 2-5 contain buttons.

01 # Create a simple graphic interface
02 #
03 import PySimpleGUI as sg
04
05 layout = [ [sg.Text("the feedback" , key="feedback")],
06            [sg.Button("FORWARD")],
07            [sg.Button("LEFT"),sg.Button("RIGHT")],
08            [sg.Button("STOP")],
09            [sg.Button("QUIT")]
10           ]
11 # Create the Window
12 window = sg.Window('My First App', layout)
13 # Event Loop to process "events"
14 while True:
15     event, values = window.read()
16     window['feedback'].Update(event) # show the button in the feedback text
17     print(event,values)
18     if event in (None, 'QUIT'):
19         break
20 window.close()

Figure 3: PySimpleGUI button example.

The PySimpleGUI sg.window() method displays a window with the title and a layout definition (line 12). The window.read() method returns events and values that have changed (line 15). The feedback text element (line 5) is given the key name feedback, which is used by the Update method to indicate which button is pressed (line 16).

Standalone Web Apps

The PySimpleGUIWeb library is excellent for creating a lightweight standalone web interface. The real beauty in PySimpleGUIWeb is that no HTML, style sheets, Ajax, or JavaScript code is required. PySimpleGUIWeb is ideal for small, single-user web interfaces, and it supports features like a tabbed interface, tables, and graphics; however, it would not be a good fit if you need a multipage-multiuser web environment.

To install PySimpleGUIWeb enter:

pip install remi
pip install pysimpleGUIweb

If I use my earlier button example, but this time use the PySimpleGUIWeb library, the code is identical, except for some added window options (Figure 4). If you are working locally on a Raspberry Pi, you can use the default sg.window settings; however, if you want to work remotely, you need to define a web server address (web_ip) and port (web_port) and to disable the auto launching of the a web browser (web_start_browser = False).

Figure 4: PySimpleGUIWeb button example.