These are a few of the adjectives I hear from people when they describe what excites them about Python. Often you can research and complete a project in a single day using Python. It does short and long term code equally well too. The code-build-run cycle time can be as short as you want to make it, perhaps single-digit seconds. Python is the perfect "impatient programmer's language".
There are many built-in packages in the standard library and PyPI reports 10,000s more that you can install with a single line of text using the pip command.
There have been a lot of GUI packages over the years with the official python GUI package being tkinter.
When it comes to GUIs, there is not currently a GUI framework available that beginners and advanced programmers alike can use to make a full-featured attractive, custom, GUI quickly. Nor, in this author's opinion, are the well-known full-featured GUI pacakages particularly "Straightforward, compact, intuitive, minimalistic, and, of course, fun". "Full featured" here means having control over the placement of individual widgets with the widget list being all of the usual widgets, label, entry, sliders, drop down menus, menu bars, etc.
If nothing existed and you could define your own GUI framework to fill this missing framework, what would be some of the characteristics for a Python GUI interface?
If there is/was, it's ones of the best well-kept secrets about Python as student and beginners post on the Internet seeking help in finding a Python GUI framework that they have a prayer of being able to use. In the r/Python subreddit, the question "What GUI Framework Should I Choose" is asked approx every 3 days. Certainly at least once a week and at times it's every day or every other day.
A large population of Python developers, data scientists, makers, and hobbiests are being left out of the Python GUI tent. Users, and developers are users too, are beyond text input and output. That ship sailed with Windows 3.1 in the 90's. Human beings enjoy using the computer with a mouse, and a GUI.
This article describes one way to enable everyone that wants to add a GUI to their program to be successful
This is a subjective view and you might disagree. But it's one based on facts. It's a fact that at the moment someone with 1 week's experience will be unable to create a GUI using tkinter, Qt, Flask, WxPython, etc. If these sorts of articles upset you, this would be an excellent time for you to surf off to some other bright shiney thing.
This article includes observations, conclusions, and recommendations that are not meant to cover or represent 100% of the possible situations. In terms of GUIs, the benchmark set is 80% of the use cases.
Corner cases exist in all areas of problems. There are "yea but what about...." questions you can ask about anything and everything in the universe. There's no attempt being made nor claimed that this proposal solves every GUI prohblem, every programmer's educational level, every runtime environment, etc.
There is also the question of how "modern", "beautiful" or "attractive" your GUI will be. Much of the attractiveness is in the hands of the user. 20% of the use cases includes fancy interfaces that perhaps a commercial product or a website desires. Animating a button isn't (yet) part of the discussion.
This architecture is targeted at user code, not library code. In other words, the person writing the code and using the code is a "user", not a person writing a library module.
To be a "GUI" in this discussion:
* A library needs to provide access to all of the well-known GUI widgets (Text, Buttons, Sliders, etc)
* Allows the user to place Widgets in any arrangement desired by the user
(i.e. they are not dumbed down nor are they templates you choose from)
* The primary use is User Interface to a Python application (as opposed to serving up web pages)
Now there's a loaded word. It's subjective to be sure, but there certain traits, patterns or pieces of code that make them more or less Pythonic "feeling".
*Few things are truly out of reach of the beginner in Python.*
Look at Threads for example. After reading the 2 pages on Threads from the Python documentation, someone within the first couple of months of starting their Python education can figure out how to create and start a thread.
There are a lot of choices for GUI libraries in Python. Based on posts I have seen over the past year in the Reddit r/LearnPython and r/Python, I believe these three packages are among the most recommended by users to posters asking for help. Maybe they're not the most downloaded, or installed, but they're all ***mentioned*** heavily. The recommendations needed to boil down to something, and this is the list of what I think are three of the more popular packages being suggested when someone asks about building a *desktop GUI* for their Python program.
Let's call them "the 3 GUI packages" for reference purposes. They may not statistically BE the top 3, but some label is needed for this group and that's the label they're getting here.
One interesting and problematic fact about the 3 GUI pacakges listed in Python is that they were not written *for* Python. They were designed and used with C++ prior to being brought over to Python. Or as is the case with tkinter, used with TCL, a scripting language. Bringing an existing GUI library into Python isn't the problem when it comes to reaching more potential Python GUI users.
The problem is that they also brought a rigid definition of how a user's GUI code is be architected. You will have these classes in your code. You will need to have a certain amount of experience/education to make something of substance.
The "preferred" (only practical) way to use these GUI packages require the end user to design and write their GUI in an object oriented manner. Pick up a book on any of these GUI libraries and you'll see in the exercises is the word Class. It's just how it is.
Sure, you can, with some effort, "get around" using classes, but it's not straightforward nor easy, a couple of the defining characteristics of being "pythonic". You shouldn't have to do this to begin with.
Think through the Python standard library and it's many packages. Do any of these packages require you to design large sections of your code in a particular way in order to use them?
Some programming languages, like C#, utilize events and callbacks heavily. Some designs also utilize callbacks. The 3 GUI packages all handle events by calling a user's callback function.
When a button is pressed in tkinter, for example, the function specified when the user created the button is called. All of the 3 GUIs work this way, calling a user's function when an event happens.
Let's take queues as an example for handling "events". In the Python library there is a `queue` module that has an object called, you guessed it, `Queue`. In some languages or libraries, a Queue object like this one would generate a callback when something arrives in the queue.
The way this `Queue` works in Python is that you `get` an item from the Queue. There are 2 modes you can use, blocking and non-blocking. Additionally, if blocking is specified, you can set a timeout value that will raise an Empty Exception when nothing is found in the queue within the timeout.
The remainder of this article will be utilizing the PySimpleGUI package's APIs and objects as a concrete way to describe the point to be made, that Python GUIs can be more Pythonic than they are today.
If you're reading this, you've likely already read about or experienced the concepts and characteristics of the 3 packages already discussed so no need to fill up the page with examples from the 3 packages. If you want to learn more about them, a Google search will turn up plenty for you to study.
Since everything's an object in Python and Python programmers are confortable using objects, use objects in a way that's logical and simple, but *don't require the user to create new object definitions of their own* (i.e. they don't have to write the word class).
In order to make a button, users *use* the `Button` object. To show some text in the window it's a `Text` object, etc. We're just talking about using these objects, just like Theads or Queues.
Python's `List` and `Dictionary` types are fundamental to say the least. When first hearing about Python and its `Lists` I honestly didn't understand what the excitement was all about. I couldn't envision that a list of stuff could make a language powerful (and popular too).
How about we define our window using nothing but lists? Everyone that programs Python knows what a list is, how to make on, and how to operate on them too. Our window's "layout" is a "list of lists". What is meant by that is that 1 "row" of a window's widgets is a list.
What we have is a list, with 2 lists inside of it. Each of the interrior lists represents 1 row of the GUI. Looking at this layout, It's probably obvious what this window will look like.
We've got our window's interrior, now let's make a window. Like other std lib calls, such as Threads, mentioned before, it's a simple object that users interact with.
Our next step will be display the window and deal with what we want our button to do. Notice that unlike the 3 GUI frameworks, our `Button` object doesn't have a callback function. How are we supposed to know when someone clicks the button?
The way we're going to get the events is using the exact same technique that our Queue example earlier did. For the queue, the call get `get`. For PySimpleGUI Windows, the call is `read`. Let's add that to our program and we'll be done.
It looks like what's being returned is a tuple. The first part is our button's text, called "the event" in PySimpleGUI, the second part is an empty dictionary. If there were input fields in this window, then the dictionary would contains the values of those fields.
This unpacks the 2 values in to 2 variables `event` representing the event that caused the `read` to return. The `values` variable contains all of the values in the input fields for the window.
\* Recall earlier in the Queue example I said the `Queue.get` model would be seen again. You just saw it in the `window.read()` call. The default action is to block on the `read`. Just like `Queue.get()` you can put a timeout value on the call so that the call is not blocking. Instead of completely blocking the block will end after the timeout and return back to you, a "block with a timeout".
Here is how you can get a window's events in the same "block with a timeout" way. In this example, the `timeout` of 100 means "block for up to 100 ms" for an event to take place, then return.
If you want a function to be called when a button is pressed in your window, then you quite simply see if the event you received is that button and then YOU make the call.
```python
event, values = window.read()
if event == 'My Button': # if the button was clicked then
my_callback('My Button', values, ....) # make your callback
Experience has shown, however, that these "callbacks" are not used by most people. Often times the event is handled right on the spot, especially if the action to take is short.
## The Fun Begins - Applying Python's Capabilities with GUIs
Since we're storing our window's GUI layout in a Python list, that means we can do fun Pythony things to create these layouts. One such activity is utilizing List Comprehensions to generate a layout.
```python
from PySimpleGUI import Text, CBox, Input, Button, Window
If this non-OOP GUI architecture is appealing to you then give PySimpleGUI a try. PySimpleGUI is relatively new, released in July 2018 and will currently "render" your GUI window **using** any of the 3 GUI packages as the backend as well as being able to show your window in your browser by using Remi as the backend.
The super-simple examples shown in this article are just that, super-simple examples. The "Simple" of PySimpleGUI does not describe the problem space, but rather the difficultly in solving your GUI problems.
