Few people run Python programs by double clicking the .py file as if it were a .exe file. When a typical user (non-programmer types) double clicks an exe file, they expect it to pop open with a window they can interact with. While GUIs, using tkinter, are possible using standard Python installations, it's unlikely many programs do this.
What if it were easy so to open a Python program into a GUI that complete beginners could do it? Would anyone care? Would anyone use it? It's difficult to answer because to date it's not been "easy" to build a custom GUI.
There seems to be a gap in the ability to add a GUI onto a Python program/script. Complete beginners are left using only the command line and many advanced programmers don't want to take the time required to code up a tkinter GUI.
There is no shortage of GUI frameworks for Python. tkinter, WxPython, Qt, Kivy are a few of the major packages. In addition, there are a good number of dumbed down GUI packages that wrap one of the major packages. These include EasyGUI, PyGUI, Pyforms, ...
The problem is that beginners (those with experience of less than 6 weeks) are not capable of learning even the simplest of the major packages. That leaves the wrapper-packages. Users will likely find it difficult or impossible to build a custom GUI layout. Or, if it's possible, pages of code are required.
PySimpleGUI attempts to address these GUI challenges by providing a super-simple, easy to understand interface to GUIs that can be easily customized. Even the most complex of GUIs are often less than 20 lines of code when PySimpleGUI is used.
What makes PySimpleGUI superior for newcomers is that the package contains the majority of the code that the user is normally expected to write. Button callbacks are handled by PySimpleGUI, not the user's code. Beginners struggle to grasp the concept of a function, expecting them to understand a call-back function in the first few weeks is a stretch.
With most GUIs arranging the GUI Widgets often requires several lines of code.... at least one or two lines per widget. PySimpleGUI uses an "auto-packer" that creates the layout for the user automatically. There is no concept of a pack nor a grid system needed to layout a GUI Window.
Finally, PySimpleGUI leverages the Python language constructs in clever ways that shortens the amount of code and returns the GUI data in a straightforward manner. When a Widget is created in a form layout, it is configured in-place, not several lines of code away. Results are returned as a simple list or a dictionary.
Most GUIs do one thing.... they collect information from the user and return it. From a programmer's viewpoint this could be summed up as a function call that looks like this:
button, values = GUI_Display(gui_layout)
What's expected from most GUIs is the button that was clicked (OK, cancel, save, yes, no, etc), and the values that were input by the user. The essence of a GUI can be boiled down into a single line of code.
This is exactly how PySimpleGUI works (for these simple kinds of GUIs). When the call is made to display the GUI, execution does no return until a button is clicked that closes the form.
There are more complex GUIs such as those that don't close after a button is clicked. These complex forms can also be created with PySimpleGUI. A remote control interface for a robot and a chat window are a couple of examples.
## The 5-Minute GUI
When is PySimpleGUI useful? Immediately, anytime you've got a GUI need. It will take under 5 minutes for you to create and try your GUI. With those kinds of times, what do you have to lose trying it?
The best way to go about making your GUI in under 5 minutes is to copy one of the GUIs from the [PySimpleGUI Cookbook](https://pysimplegui.readthedocs.io/en/latest/cookbook/). Follow these steps:
* Find a GUI that looks similar to what you want to create
* Copy code from Cookbook
* Paste into your IDE and run
Let's look at the first recipe from the book
import PySimpleGUI as sg
# Very basic form. Return values as a list
form = sg.FlexForm('Simple data entry form') # begin with a blank form
layout = [
[sg.Text('Please enter your Name, Address, Phone')],
That 5-minute estimate wasn't the time it takes to copy and paste the code from the Cookbook. You should be able to modify the code within 5 minutes in order to get to your layout, assuming you've got a straightforward layout.
Widgets are called Elements in PySimpleGUI. This list of Elements are spelled exactly as you would type it into your Python code.
### Core Element list
```
Text
InputText
Multiline
InputCombo
Listbox
Radio
Checkbox
Spin
Output
SimpleButton
RealtimeButton
ReadFormButton
ProgressBar
Image
Slider
Column
```
You can also have short-cut Elements. There are 2 types of shortcuts. One is simply other names for the exact same element (e.g. T instead of Text). The second type configures an Element with particular setting, sparing the programmer from specifying all of the parameters (e.g. Submit is a button with the text "Submit" on it).
### Shortcut list
T = Text
Txt = Text
In = InputText
Input = IntputText
Combo = InputCombo
DropDown = InputCombo
Drop = InputCombo
A number of common buttons have been implemented as shortcuts. These include:
### Button Shortcuts
FolderBrowse
FileBrowse
FileSaveAs
Save
Submit
OK
Ok
Cancel
Quit
Exit
Yes
No
The more generic button functions, that are also shortcuts
### Generic Buttons
SimpleButton
ReadFormButton
RealtimeButton
These are all of the GUI Widgets you have to choose from. If it's not in this list, it doesn't go in your form layout.
### GUI Design Pattern
The stuff that tends not to change in GUIs are the calls that setup and show the Window. It's the layout of the Elements that changes from one program to another. This is the code from above with the layout removed:
import PySimpleGUI as sg
form = sg.FlexForm('Simple data entry form')
# Define your form here (it's a list of lists)
button, values = form.LayoutAndRead(layout)
The flow for most GUIs is:
* Create the Form object
* Define GUI as a list of lists
* Show the GUI and get results
These are line for line what you see in design pattern.
### GUI Layout
To create your custom GUI, first break your form down into "rows". You'll be defining your form one row at a time. Then for each for, you'll be placing one Element after another, working from left to right.
The result is a "list of lists" that looks something like this:
Once you have your layout complete and you've copied over the lines of code that setup and show the form, it's time to look at how to display the form and get the values from the user.
This is the line of code that displays the form and provides the results:
button, values = form.LayoutAndRead(layout)
Forms return 2 values, the text of the button that was clicked and a ***list of values*** the user entered into the form.
If the example form was displayed and the user did nothing other than click the OK button, then the results would have been:
button == 'OK'
values == [False, False]
Checkbox Elements return a value of True/False. Because these checkboxes defaulted to unchecked, the values returned were both False.
## Displaying Results
Once you have the values from the GUI it would be nice to check what values are in the variables. Rather than print them out using a `print` statement, let's stick with the GUI idea and output to a window.
PySimpleGUI has a number of Message Boxes to choose from. The data passed to the message box will be displayed in a window. The function takes any number of arguments. Simply indicate all the variables you would like to see in the call.
The most-commonly used Message Box in PySimpleGUI is MsgBox. To display the results of the previous example, one would write:
MsgBox('The GUI returned:', button, values)
## Putting It All Together
Now that you know the basics, let's put together a form that contains as many PySimpleGUI's elements as possible. Also, just to give it a nice look, we'll change the "look and feel" to a green and tan color scheme.
import PySimpleGUI as sg
sg.ChangeLookAndFeel('GreenTan')
form = sg.FlexForm('Everything bagel', default_element_size=(40, 1))
Each parameter to the message box call is displayed on a new line. There are actually 2 lines of text in the message box. The second line is very long and wrapped a number of times
Take a moment and pair up the results values with the GUI to get an understanding of how results are created and returned.
If you have a script that uses the command line, you don't have to abandon it in order to add a GUI. An easy solution is that if there are zero parameters given on the command line, then the GUI is run. Otherwise, execute the command line as you do today.
This kind of logic is all that's needed:
if len(sys.argv) == 1:
# collect arguments from GUI
else:
# collect arguements from sys.argv
The easiest way to get a GUI up and running quickly is to copy and modify one of the Recipes from the [PySimpleGUI Cookbook](https://pysimplegui.readthedocs.io/en/latest/cookbook/)
Have some fun! Spice up the scripts you're tired of running by hand. Spend 5 or 10 minutes playing with the demo scripts. You may find one already exists that does exactly what you need. If not, you will find it's 'simple' to create your own. If you really get lost, you've only invested 10 minutes.
