magicgui 🧙🔗

License Version Python Version

build GUIs from python functions, using magic.


pip install magicgui


You will need to have a supported GUI backend also installed in your environment. Currently, the only supported backend is Qt, via qtpy (but open an issue if you would like to see a different backend supported).

To use with Qt, you will also need to have either PyQt5 or PySide2 installed in your environment. For example:

pip install magicgui pyside2


The core feature of magicgui is the @magicgui decorator, which, when used to decorate a function, will autogenerate a graphical user interface (GUI) by inspecting the function signature and adding an appropriate GUI widget for each argument. Argument types are taken from type hints if provided, or inferred using the type of the default value. The resulting GUI Class is added to the function as a new attribute named Gui.

import math
from enum import Enum
from magicgui import magicgui

# dropdown boxes are best made by creating an enum
class Medium(Enum):
    Glass = 1.520
    Oil = 1.515
    Water = 1.333
    Air = 1.0003

# decorate your function with the ``@magicgui`` decorator
def snells_law(aoi=30.0, n1=Medium.Glass, n2=Medium.Water, degrees=True):
    aoi = math.radians(aoi) if degrees else aoi
        result = math.asin(n1.value * math.sin(aoi) / n2.value)
        return math.degrees(result) if degrees else result
    except ValueError:
        # beyond the critical angle
        return "Total internal reflection!"

# your function will have a new attribute "Gui"
# calling it instantiates the widget (and, optionally, shows it)
snell_gui = snells_law.Gui(show=True)

et voilà🔗

two-way data binding🔗

The fun is just beginning! The new snell_gui object has attributes named after each of the function parameters. As you make changes in your new GUI, these attributes of the snell_gui will be kept in sync. For instance, change the first dropdown menu from “Glass” to “Oil”, and the corresponding parameter changes on snell_gui:

In [2]: snell_gui.n1
Out[2]: <Medium.Oil: 1.515>

it goes both ways: change a parameter in the console and it will change in the GUI:

In [3]: snell_gui.aoi = 47

In [4]: print(snell_gui)
<MagicGui: snells_law(aoi=47.0, n1=Medium.Glass, n2=Medium.Water, degrees=True)>

calling the function🔗

We can call our function in a few ways:

  1. Because we provided the call_button argument to the magicgui decorator, a new button was created that will execute the function with the current gui parameters when clicked. (at the moment, we haven’t hooked anything up to it, so it won’t be all that interesting!)

  2. We can also directly call the original function. Now however, the current values from the GUI will be used as the default values for any arguments that are not explicitly provided to the function:

    In [5]: snells_law()
    Out[5]: 56.22
    # Note: calling the gui object has the same result
    # as calling the original function:
    In [6]: snell_gui()
    Out[6]: 56.22
  3. You can still override positional or keyword argumnets in the original function, just as you would with a regular function. (Note: calling the function with values that differ from the GUI will not set the values in the GUI… It’s just a one-time call).

    # in radians, overriding the value for the second medium (n2)
    In [7]: snells_law(0.8, n2=Medium.Air, degrees=False)
    Out[7]: 'Total internal reflection!'

connecting events🔗

function calls🔗

Usually in a GUI you are looking for something to happen as a result of calling the function. The original function (and the gui instance) will have a new called attribute (a Qt Signal) that you can connect to an arbitrary callback function:

def my_callback(result):
    # do something with the result, trigger other events, etc...


Now when you call snells_law() or snell_gui(), or click the calculate button in the gui, my_callback will be called with the result of the calculation.

parameter changes🔗

You can also listen for changes on individual function parameters by connecting to the <parameter>_changed signal:

# whenever the current value for n1 changes, print it to the console:

This signal will be emitted regardless of whether the parameter was changed in the GUI or via by directly setting the paramaeter on the gui instance.

In [8]: snell_gui.n1 = Medium.Air


Remember, @decorators are just syntactic sugar: you don’t have to use magicgui to decorate your function declaration. You can also just call it with your function as an argument:

# the decorator in the first example could be replaced with this:
magic_snell = magicgui(snells_law, call_button='calculate')
snell_gui = magic_snell.Gui(show=True)

configuration and advanced usage🔗

The @magicgui decorator takes a number of options that allow you to configure the GUI and it’s behavior. See configuration for more information.