Python3 tkinter analog gauge

Question

I'm trying to use an analog gauge for my tkinter/ttk GUI written in Python 3.6.

I want to display volt and psi values.

My research so far led me to this (linuxcnc/pyvcp?), this (perl/tk) and this (tk).

Is there any chance I could integrate on of these three or should I try to implement my own gauge by using tkinter.Canvas ?

Answer 1

I have translated the 3rd one in python:

import tkinter as tk
from math import pi, cos, sin


class Meter(tk.Frame):
    def __init__(self, master=None, **kw):
        tk.Frame.__init__(self, master, **kw)

        self.meter = []
        self.angle = []
        self.var = tk.IntVar(self, 0)

        self.canvas = tk.Canvas(self, width=200, height=110,
                                borderwidth=2, relief='sunken',
                                bg='white')
        self.scale = tk.Scale(self, orient='horizontal', from_=0, to=100, variable=self.var)

        for j, i in enumerate(range(0, 100, 5)):
            self.meter.append(self.canvas.create_line(100, 100, 10, 100,
                                                      fill='grey%i' % i,
                                                      width=3,
                                                      arrow='last'))
            self.angle.append(0)
            self.canvas.lower(self.meter[j])
            self.updateMeterLine(0.2, j)

        self.canvas.create_arc(10, 10, 190, 190, extent=108, start=36,
                               style='arc', outline='red')

        self.canvas.pack(fill='both')
        self.scale.pack()

        self.var.trace_add('write', self.updateMeter)  # if this line raises an error, change it to the old way of adding a trace: self.var.trace('w', self.updateMeter)
        self.updateMeterTimer()

    def updateMeterLine(self, a, l=0):
        """Draw a meter line (and recurse for lighter ones...)"""
        oldangle = self.angle[l]
        self.angle[l] = a
        x = 100 - 90 * cos(a * pi)
        y = 100 - 90 * sin(a * pi)
        self.canvas.coords(self.meter[l], 100, 100, x, y)
        l += 1
        if l < len(self.meter):
            self.updateMeterLine(oldangle, l)

    def updateMeter(self, name1, name2, op):
        """Convert variable to angle on trace"""
        mini = self.scale.cget('from')
        maxi = self.scale.cget('to')
        pos = (self.var.get() - mini) / (maxi - mini)
        self.updateMeterLine(pos * 0.6 + 0.2)

    def updateMeterTimer(self):
        """Fade over time"""
        self.var.set(self.var.get())
        self.after(20, self.updateMeterTimer)


if __name__ == '__main__':
    root = tk.Tk()
    meter = Meter(root)
    meter.pack()
    root.mainloop()

The same but without the fading effect for the arrow:

class Meter(tk.Frame):
    def __init__(self, master=None, **kw):
        tk.Frame.__init__(self, master, **kw)

        self.var = tk.IntVar(self, 0)

        self.canvas = tk.Canvas(self, width=200, height=110,
                                borderwidth=2, relief='sunken',
                                bg='white')
        self.scale = tk.Scale(self, orient='horizontal', from_=0, to=100, variable=self.var)

        self.meter = self.canvas.create_line(100, 100, 10, 100,
                                             fill='black',
                                             width=3,
                                             arrow='last')
        self.angle = 0
        self.updateMeterLine(0.2)

        self.canvas.create_arc(10, 10, 190, 190, extent=108, start=36,
                               style='arc', outline='red')

        self.canvas.pack(fill='both')
        self.scale.pack()

        self.var.trace_add('write', self.updateMeter)  # if this line raises an error, change it to the old way of adding a trace: self.var.trace('w', self.updateMeter)

    def updateMeterLine(self, a):
        """Draw a meter line"""
        self.angle = a
        x = 100 - 90 * cos(a * pi)
        y = 100 - 90 * sin(a * pi)
        self.canvas.coords(self.meter, 100, 100, x, y)

    def updateMeter(self, name1, name2, op):
        """Convert variable to angle on trace"""
        mini = self.scale.cget('from')
        maxi = self.scale.cget('to')
        pos = (self.var.get() - mini) / (maxi - mini)
        self.updateMeterLine(pos * 0.6 + 0.2)

Answer 2

I created a package called tk_tools that has one of these analog gauges.

pip install tk_tools

Source: https://github.com/slightlynybbled/tk_tools

Documentation: https://tk-tools.readthedocs.io/en/latest/docs/widgets/#rotaryscale

You are looking for the RotaryScale widget. An example of use can be found in examples/rotary_scale.py. The short version:

import tkinter as tk
import tk_tools

root = tk.Tk()

p = tk_tools.RotaryScale(root, max_value=100.0, unit='psi')
p.grid()

p.set_value(32.7)

root.mainloop()