What language are your apps written in? Generally the best options are:

1. Qt (C++) or PyQt (Python wrapper if you hate yourself). Old school desktop GUI. Works extremely well though.
2. Web based, then you can pick from a gazillion frameworks, most popular is React. You generally have a Typescript based frontend and a backend in whatever language you want. The downside is you have to deal with the frontend/backend communication which can be a pain.

There’s also Flutter which is pretty nice, but again you have to use Dart for the GUI so if the rest of your app is in another language you’ll have some friction.

But yeah, I would say the language you want to write your “business logic” in is the biggest factor to choosing. Also if you care about exposing your app over the web.

Blazor is incredibly versatile in terms of where and how you run it. The UI is in HTML and CSS, the generated runtime bindings in JavaScript, but you can code the backend as well as frontend logic in C# / .NET / Razor template files.

It can render on the server or client, even work offline with WebAssembly and Service Worker, and dynamically switch between or combine them.

You can also integrate it into Windows Forms, WPF, or multi-platform .NET MAUI with Webview2, which will render “as a website” while still binding and integrating into other platform UI and code.

Your goals of “neat little GUI” and “as portable as possible” may very well be opposing each other.

Main questions are what do you have (technologies); what are you constraints, and what do you need. Different tech has different UI tech. Overall, most GUI programming is a hassle or mess.

If you want to dip your toes, use the tech you like, and look for simple GUI techs first. Don’t try to do everything/all platforms at once first.

What languages are you wanting to use, the combination between toolkit and language can make a big difference to your experience.

There are a lot of interesting options out there that aren’t top of people’s minds too. For instance Lazarus, and Flutter. Both can do cross platform.

Understand what tradeoffs different solutions make, then inform your decision on that. A fairly general principle for example is that the more cross-platform compatible a solution is, the less well-suited it will be for any given platform in terms of looks/behavior/performance. This may or may not matter for what you’re building.

There are inherent qualities to some solutions (for example, a particular library may make for good solutions on a certain platform), and some qualities will be situational (a particular library is good for you because you happen to know the language/patterns/framework/whatever).

I personally like to build things in Kotlin and Jetpack Compose, but that’s because I primarily build mobile apps for Android and I like the reactive UI paradigm that underpins this library along with the language that it’s written in. I would perhaps reconsider if I were building a desktop app (not as well supported), and definitely reconsider if I were building a web app (definitely a poor fit).

So yeah, start with what you’re building and what its requirements are. Then think about what you already know, and finally put those together when evaluating a UI solution.

If you only need something like buttons, sliders and other simpel, non-user-account driven stuff, than Streamlit.io is an option.

A simple requirements.txt and shipping your Python app with an .bat or .sh that just does:

open venv start main.py in venv closr venv

should be a hood intermediate step from cli script to gui

If you do want to go the web route, I’d highly recommend avoiding SPAs and going with https://htmx.org/ instead. Much simpler, less code, entirely driven by your backend, while still giving you the ability to make nice interactive applications.

As a bonus, since you presumably have been working with Python anyway, the author of htm has a whole book online walking you through building an app using htmx and Flask, a web framework for Python: https://hypermedia.systems/book/contents/

be as portable as possible

This is important to me, which narrows down my options quite a bit.

Electron is portable across desktop OS, but unacceptably bloated (I don’t want my users to have to deal with that) and buggy (I don’t want to deal with that).

wxWidgets and various similar wrapper libraries exist, but on Linux most of them wrap Gtk, which in recent years has become very opinionated in UI directions that I find intolerable.

A few new cross-platform GUI toolkits have been appearing recently, but I’ve found all of them suffer from poor text handling, anemic widget sets, or very out-of-place look and feel (especially keyboard navigation) relative to native applications.

That leaves Qt as my only reasonable choice, at least for now. This is mostly okay, as it does a wonderful job all around. My main complaint is that using the full power of its widgets and libraries means I’m restricted to a handful of languages: C++, Python, and maybe one or two minor ones like D. Its declarative API (Qt Quick) seems to be getting more language bindings, though, so simpler apps might be possible in other languages.

Note that the landscape is different for mobile apps. I don’t have a recommendation for those.

Time, experience and a lot of mistakes. Everyone who has been programming/scripting has made their fair share of mistakes along their journey.

Sometimes you just have to pick one, start it and see how it goes.

JS is optional, it’s unpleasant, as well as use a bunch of fat frameworks. But now there is HTMX, which makes any GUI without JS, pure HTML combined with some Bootstrap 5 is enough. I write in Go, it has a great built-in template, and it’s enough for any level of GUI

Making a web app is a mistake 9 times out of 10, particularly when dealing with larger datasets. Because you’re in physics, you probably want to skills you’re learning to be transferable into physics and data science in general.

I recommend starting with python (if you know it already, awesome), then checking out pyqtgraph – there’s a bunch of demo apps that come with the package and you can use those as launch points. This will be your gateway into pyqt/pyside and legit desktop application development. Later, if you learn C++, you can transition into Qt (and still use all the power of the toolkit and the skills are transferable), or into raw C++ which is amazing for numerical computing.

You may be interested in MatPlotLib for Python and maybe something like mpld3 to get it to the browser. I’ve been trying a few frameworks out recently, so I’ve seen a few Python options that use the browser as their main window. NiceGUI has a browser front end and graphing that may be able to do what you want as well, but there are others you can find. You might look for tutorials on YouTube if you’re having trouble deciding, to see how difficult it is to learn and work with. If you know any c++, there’s a long but descriptive list of frameworks available on GitHub, sorted into categories, that could help narrow those options down. It probably depends a lot on what you already know, but there are more options than JavaScript. You have a lot of good keywords to narrow down a search. <Your language> GUI or graphing framework browser frontend open source (no license)

As a C# programmer, I like to make desktop GUIs with WPF or Avalonia. Web is also possible with asp.net, but I don’t like it as much.

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