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function in a function

The new function contains other functions

With all the code gathered together in a new function, the code for the
create_gui() function looks like this:

from tkinter import *
import pygame
This function is
LOCAL to the def create_gui(app, mixer, sound_file): Note: when this function is called,
“create_gui()” it is expecting three parameters.
function. def track_toggle():
if track_playing.get() == 1:
These are the event
track.play(loops = -1)
else: handlers, which are
This function is track.stop() linked to the “command”
parameter of each widget.
LOCAL, too.
def change_volume(v):
When this track.set_volume(volume.get())
function is
called, it starts
executing from track = mixer.Sound(sound_file)
here. track_playing = IntVar()

track_button = Checkbutton(app, variable = track_playing,
command = track_toggle, text = sound_file)
track_button.pack(side = LEFT)
As always, volume = DoubleVar()
the calls to
volume.set(track.get_volume())
“pack()” add volume_scale = Scale(variable = volume, from_ = 0.0, to = 1.0,
the widgets to resolution = 0.1, command = change_volume,
the GUI. label = "Volume", orient = HORIZONTAL)

volume_scale.pack(side = RIGHT)

A function-in-a-
Do you notice anything strange? The new function actually has two other
functions inside it. Python (and several languages) lets you create local function is called
functions. A local function is just a function inside a function.
a local function.
Let’s see why they’re important for the DJ’s program.

356 Chapter 10