Python Kivy graph code only gives 'Python has stopped working' as error message

Question

I'm trying to play around with a real-time kivy graph using the kivy_garden.graph module. However, when i run the following code, I get no error message other than a popup stating 'Python has stopped working'. Once I press cancel on that, I get Process finished with exit code -1073741819 (0xC0000005). Here's my code:

from math import sin
from kivy_garden.graph import Graph, MeshLinePlot
from kivy.app import App
from kivy.uix.boxlayout import BoxLayout
from kivy.clock import Clock


class MyApp(App):
    plot = MeshLinePlot(color=[1, 0, 0, 1])

    graph = Graph(xlabel='X', ylabel='Y', x_ticks_minor=5,
        x_ticks_major=25, y_ticks_major=1,
        y_grid_label=False, x_grid_label=False, padding=5,
        x_grid=False, y_grid=False, xmin=-0, xmax=100, ymin=-1, ymax=1,)

    def build(self):

        box = BoxLayout()
        box.add_widget(self.graph)
        Clock.schedule_interval(self.update_points, 1/60.)
        Clock.schedule_interval(self.update_xaxis, 1/60.)

        return box

    def update_xaxis(self,*args):
        self.graph.xmin = 0
        self.graph.xmax = 100

    def update_points(self, *args):
        #self.plot.points = [(i,i)]

        self.plot.points = [(x, sin(x / 10.)) for x in range(0, 101)]





MyApp().run()

My other kivy apps are running just fine on the same python installation, so I'm inclined to believe that there's something wrong with my code.

Thanks for any and all help!

score 2 · Accepted Answer · answered Nov 23 '21 at 18:54

Strange as it may seem, it appears that your Graph() and MeshLinePlot() calls must be in the opposite order:

class MyApp(App):
    graph = Graph(xlabel='X', ylabel='Y', x_ticks_minor=5,
        x_ticks_major=25, y_ticks_major=1,
        y_grid_label=False, x_grid_label=False, padding=5,
        x_grid=False, y_grid=False, xmin=-0, xmax=100, ymin=-1, ymax=1,)
    plot = MeshLinePlot(color=[1, 0, 0, 1])

    def build(self):
        self.graph.add_plot(self.plot)
        box = BoxLayout()
        box.add_widget(self.graph)
        Clock.schedule_interval(self.update_points, 1/60.)
        Clock.schedule_interval(self.update_xaxis, 1/60.)

        return box

And you were missing the self.graph.add_plot(self.plot) line.

hc_dev · Answer 2 · 2021-11-23T19:17:19.993

Research

The error-code 0xC0000005 might be a Windows related error, known as Access Violation. See Process finished with exit code -1073741819 (0xC0000005) Pycharm

On the other side any threading-related seems suspicious. So, searched for Clock.schedule_interval and found an answer that suggested to avoid duplicate scheduling. See Kivy - Trying to Understand Clock.schedule_interval.

To avoid duplicate calls, they propose to unschedule before scheduling again.

# First, schedule once.
event = Clock.schedule_once(my_callback, 0)

# Then, in another place you will have to unschedule first to avoid duplicate call. Then you can schedule again.
Clock.unschedule(event)
event = Clock.schedule_once(my_callback, 0)

I can't tell what your separately scheduled update-events are for, but it looks like they can be combined to one update-callback.

Python Kivy graph code only gives 'Python has stopped working' as error message

2 Answers2

Research