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Background

Why PySimpleGUI Came to Be

Feel free to skip all this if you don't care to know the backstory and reasons behind decisions.

There was a project looming and a GUI was needed. It wasn't a very complex GUI so thus began a search for a simplified GUI package that would enable me to work with tkinter easier. I found a few, and they were pretty popular too, but they lacked the full-compliment of Widgets and it was impossible to define my own window using those widgets.

A whacky idea came to mind... what if I wrote a simplified GUI and then used THAT to write my application. It would be a lot less code and it would be "easy" to write my application then. And that is exactly what was done.

First an early version of PySimpleGUI was written that had a subset of the Elements available today. It had just enough for my application. Then I wrote my application in PySimpleGUI.

Thus PySimpleGUI was born out of necessity and it's been the necessity of others that have helped evolve it into the package it is today. It would not be 1/2 as good without the help of the community.

Once PySimpleGUI was done, it was time to start working on "the ports". And, of course, also this documentation.

The Non-OO and Non-Event-Driven Model

The two "advanced concepts" that beginning Python students have with GUIs are the use of classes and callbacks with their associated communication and coordination mechanisms (semaphores, queues, etc)

How do you make a GUI interface easy enough for first WEEK Python students?

This meant classes could be used to build and use it, but classes can not be part of the code the user writes. Of course, an OO design is quite possible to use with PySimpleGUI, but it's not a requirement. The sample code and docs stay away from writing new classes in the user space for the most part.

What about those pesky callbacks? They're difficult for beginners to grasp and they're a bit of a pain in the ass to deal with. The way PySimpleGUI got around events was to utilize a "message passing" architecture instead.

Instead of a user function being called when there's some event, instead the information is "passed" to the user when they call the function Window.read()

Everything is returned through this Window.read call. Of course the underlying GUI frameworks still perform callbacks, but they all happen inside of PySimpleGUI where they are turned into messages to pass to you.

All of the boilerplate code, the event handling, widget creation, frames containing widgets, etc, are exactly the same objects and calls that you would be writing if you wrote directly in tkinter, Qt, etc. With all of this code out of the way and done for you, that leaves you with the task of doing something useful with the information the user entered. THAT, after all, is the goal here.... getting user information and acting on it.

The full complement of Widgets are available to you via PySimpleGUI Elements. And those widgets are presented to you in a unique and fun way.

The Result

A GUI that's appealing to a broad audience that is highly customizable, easy to program, and is solid with few bugs and rarely crashes (99% of the time it's some other error that causes a crash).

PySimpleGUI is becoming more and more popular. The number of installs and the number of successes grows daily. Pip installs have exceeded 350,000 in the first year of existence. Over 300 people a day visit the GitHub and the project has 1,800 stars (thank you awesome users!)

The number of ports is up to 4. The number of integrations with other technologies is constantly being expanded. It's a great time to try PySimpleGUI! You've got no more than 5 or 10 minutes to lose.

Caution is needed, however, when working with the unfinished ports. PySimpleGUI, the tkinter version, is the only fully complete port. Qt is next. All of its Elements are completed, but not all of the options of each element are done. PySimpleGUIWeb is next in order of completeness and then finally PySimpleGUIWx.

Design Goals

With the developer being the focus, the center of it all, it was important to keep this mindset at all times, including now, today. Why is this such a big deal? Because this package was written so that the universe of Python applications can grow and can include EVERYONE into the GUI tent.

Up in 5 minutes

Success #1 has to happen immediately. Installing and then running your first GUI program. FIVE minutes is the target. The Pip install is under 1 minute. Depending on your IDE and development environment, running your first piece of code could be a copy, paste, and run. This isn't a joke target; it's for real serious.

Beginners and Advanced Together

Design an interface that both the complete beginner can understand and use that has enough depth that an advanced programmer can make some very nice looking GUIs amd not feel like they're playing with a "toy".

Success After Success

Success after success.... this is the model that will win developer's hearts. This is what users love about PySimpleGUI. Make your development progress in a way you can run and test your code often. Add a little bit, run it, see it on your screen, smile, move on.

Copy, Paste, Run.

The Cookbook and Demo Programs are there to fulfill this goal. First get the user seeing on their screen a working GUI that's similar in some way to what they want to create.

If you're wanting to play with OpenCV download the OpenCV Demo Programs and give them a try. Seeing your webcam running in the middle of a GUI window is quite a thrill if you're trying to integrate with the OpenCV package.

"Poof" instant running OpenCV based application == Happy Developer

Make Simpler Than Expected Interfaces

The Single Line Progress Meter is a good example. It requires one and only 1 line of code. Printing to a debug window is as easy as replacing print with sg.Print which will route your console output to a scrolling debug window.

Be Pythonic

Be Pythonic...

This one is difficult for me to define. The code implementing PySimpleGUI isn't PEP8 compliant, but it is consistent. The important thing was what the user saw and experienced while coding, NOT the choices for naming conventions in the implementation code. The user interface to PySimpleGUI now has a PEP8 compliant interface. The methods are snake_case now (in addition to retaining the older CamelCase names)

I ended up defining it as - attempt to use language constructs in a natural way and to exploit some of Python's interesting features. It's Python's lists and optional parameters make PySimpleGUI work smoothly.

Here are some Python-friendly aspects to PySimpleGUI:

  • Windows are represented as Python lists of Elements
  • Return values are an "event" such a button push and a list/dictionary of input values
  • The SDK calls collapse down into a single line of Python code that presents a custom GUI and returns values should you want that extreme of a single-line solution
  • Elements are all classes. Users interact with elements using class methods but are not required to write their own classes
  • Allow keys and other identifiers be any format you want. Don't limit user to particular types needlessly.
  • While some disagree with the single source file, I find the benefits greatly outweigh the negatives

Lofty Goals

Teach GUI Programming to Beginners

By and large PySimpleGUI is a "pattern based" SDK. Complete beginners can copy these standard design patterns or demo programs and modify them without necessarily understanding all of the nuts and bolts of what's happening. For example, they can modify a layout by adding elements even though they may not yet grasp the list of lists concept of layouts.

Beginners certainly can add more if event == 'my button': statements to the event loop that they copied from the same design pattern. They will not have to write classes to use this package.

Capture Budding Graphic Designers & Non-Programmers

The hope is that beginners that are interested in graphic design, and are taking a Python course, will have an easy way to express themselves, right from the start of their Python experience. Even if they're not the best programmers they will be able express themselves to show custom GUI layouts, colors and artwork with ease.

Fill the GUI Gap (Democratize GUIs)

There is a noticeable gap in the Python GUI solution. Fill that gap and who knows what will happen. At the moment, to make a traditional GUI window using tkinter, Qt, WxPython and Remi, it takes much more than a week, or a month of Python education to use these GUI packages.

They are out of reach of the beginners. Often WAY out of reach. And yet, time and time again, beginners that say they JUST STARTED with Python will ask on a Forum or Reddit for a GUI package recommendation. 9 times out of 10 Qt is recommended. (smacking head with hand). What a waste of characters. You might as well have just told them, "give up".

Is There a There?

Maybe there's no "there there". Or maybe a simple GUI API will enable Python to dominate yet another computing discipline like it has so many others. This is one attempt to find out. So far, it sure looks like there's PLENTY of demand in this area.