Creating User Interfaces in Python using PySimpleGUI

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Introduction

PySimpleGUI is a Python package which can be used to develop user-interfaces with the simplest code. In spite of being simple it can be used to create complex and sophisticated user-interfaces. Any programmer, even if he is new to Python can easily learn PySimpleGUI and start creating Python applications with good looking user-interfaces within minutes.

Background

PySimpleGUI currently supports 4 GUI frameworks:

1. PySimpleGUI
2. PySimpleGUIQt
3. PySimpleGUIWx
4. PySimpleGUIWeb

Porting GUI from one framework to another can be done with very few changes. Some features may be supported by one framework but not by others, but overall, porting from one framework to another is easy with minimal changes in code. The framework to be used can be specified using the import statement. For example, to use PySimpleGUI, we can write import PySimpleGUI as sg  and to use PySimpleGUIQt, we can write import PySimpleGUIQt as sg and to use PySimpleGUIWeb, we can write import PySimpleGUIWeb as sg.

Using the code

Like other packages, PySimpleGUI can be installed using the pip command as follows:

pip install pysimplegui --user

To install PySimpleGUIWeb, the following command can be used:

pip install pysimpleguiweb --user

Layouts:

A layout is defined in PySimpleGUI using a List of Lists. Each list inside the main list defines one row. Each row consists of user-interface elements which are rendered on a single line.

Following are some of the commonly required user-interface elements than can be created in PySimpleGUI.

• sg.Text: To render constant text.
• sg.InputText: To accept input  at runtime.
• sg.Checkbox: To display a checkbox.
• sg.Radio: To display a radio button.
• sg.Combo: To display a list of items as a combobox from which only one element can be selected.
• sg.Listbox: To display a list of items as a listbox. Setting select_mode="multiple" attributeallows selecting multiple elements.

For example the following code can be used to render a typical user-interface:

layout = [
                [sg.Text("Select a theme: ",size=(15,1)),sg.Combo(sg.theme_list(),key="t",default_value="BlueMono",size=(10,1))],
                [sg.Text("Enter your name: ",size=(15,1)),sg.InputText(key="n",size=(10,1))],
                [sg.Checkbox("Capitalize",key="c",size=(15,1))],
                [sg.Text("Choose your gender: ",size=(15,1)),sg.Radio("Male","g",True,key="g1"),sg.Radio("Female","g",key="g2")],
                [sg.Text("Choose your qualification: ",size=(15,1)),sg.Combo(qualifications_list,key="q",default_value="Graduate",size=(15,3))],
                [sg.Text("Choose your hobbies: ",size=(15,1)),sg.Listbox(hobbies_list,key="h",select_mode="multiple",size=(15,3))],
                [sg.Button("Show",size=(15,1)),sg.Button("Reset",size=(15,1))]
             ]
window = sg.Window("Controls",layout)

The first row in the above layout consists of a combo box containing all available themes, obtained using the sg.theme_list() function. Other rows define other user interface elements. The sg.Window is used to create a window with the title as "Controls" and having the specified layout. Its output is as follows:

Event Handling:

An event loop is required to process events and read the inputs entered at runtime. The event loop can be created as follows:

while True:
        event,values = window.read()
        if event == sg.WINDOW_CLOSED:
           break
        if event == "Show":
           name = values["n"].upper() if values["c"] else values["n"]
           gender = "Male" if values["g1"] else "Female"
           qualification = values["q"]
           hobbies = ""
           for h in values["h"]:
                hobbies = hobbies + h + ","
           hobbies = hobbies.rstrip(",")
           details = "Name: " + name + "\n"
           details = details + "Gender: " + gender + "\n"
           details = details + "Qualification: " + qualification + "\n"
           details = details + "Hobbies: " + hobbies + "\n"
           sg.theme(values["t"])
           sg.popup(details,title="Details")
        if event == "Reset":
           window["n"].update("")
           window["c"].update(False)
           window["g1"].update(True)
           window["q"].update("Graduate")
           window["h"].update(hobbies_list)
window.close()

In the above code, the information about the button clicked or wiindow closed events and the data entered are obtained using the window.read() function. If the window close button is clicked, the sg.WINDOW_CLOSED event is fired, which causes the control to break out of the event loop and the window is closed using the close() function.  If the "Show" button is clicked, the "Show" event is fired, in which all data entered on the form is collected using the values dictionary and dispalyed in a popup window using the popup() function. If the "Reset" button is clicked, the "Reset" event is fired, in which all controls are reset to their default values using the update() function. In the "Show" event, the currently selected theme is applied using the sg.theme() function.

 

Themes: Themes can be used in PySimpleGUI to display colorful and more beautiful windows using the shortest possible code. The following line of code, creates a combo box filled with all available themes.

sg.Combo(sg.theme_list(),key="t",default_value="BlueMono",size=(10,1))

To apply the selected theme from the combo box, the following code can be used.

sg.theme(values["t"])

All available themes can be previewed using the sg.theme_previewer() function as follows.

import PySimpleGUI as sg
sg.theme_previewer()

The above code produces the following output.

Points of Interest

I hope the above discussion is helpful to readers and leads more programmers to use PySimpleGUI.