Graphing with Tkinter

Let us wrap up this project by looking at the graphing abilities of the Tkinter canvas widget.

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In this recipe we will see how we can plot:

  • Pie chart
  • Scatter chart
  • Bar graph
  • Embedding matplotlib graphs

Let's look at the pie chart first:

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  1. You can easily create pie charts in Tkinter using the Canvas widget's create_arc method. A sample Pie Chart code is provided in 7.08 pie chart.py:
    import Tkinter
root = Tkinter.Tk()
def prop(n): 
    return 360.0 * n / 1000

Tkinter.Label(root, text='Pie Chart').pack()
c = Tkinter.Canvas(width=154, height=154)
c.pack()
c.create_arc((2,2,152,152), fill="#FAF402", outline="#FAF402", start=prop(0), extent = prop(200))
c.create_arc((2,2,152,152), fill="#00AC36", outline="#00AC36", start=prop(200), extent = prop(400))
c.create_arc((2,2,152,152), fill="#7A0871", outline="#7A0871", start=prop(600), extent = prop(50))
c.create_arc((2,2,152,152), fill="#E00022", outline="#E00022", start=prop(650), extent = prop(200))
c.create_arc((2,2,152,152), fill="#294994", outline="#294994",  start=prop(850), extent = prop(150))
root.mainloop()

    The description of the code is as follows:

    • Each portion of the pie chart is drawn by changing the two following create_arc options:

      start: This option specifies the start angle. Default is 0.0.

      extent: This option specifies the size of arc relative to the start angle. Default is 90.0.

  2. Next, we'll plot a sample scatter chart:
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    Similarly, we can use create_line to draw the x and y axes and create_oval to draw the scatter plots, as shown in the preceding screenshot here. A sample scatter plot code is provided in the 7.09 scatter plot.py Python file:

    import Tkinter
import random
root = Tkinter.Tk()
c = Tkinter.Canvas(root, width=350, height=280, bg='white')
c.grid()
#create x-axis
c.create_line(50, 250, 300, 250, width=3)
for i in range(12):
    x = 50 + (i * 20)
c.create_text(x, 255, anchor='n', text='%d'% (20*i))
# create y-axis
c.create_line(50, 250, 50, 20, width=3)
for i in range(12):
    y = 250 - (i * 20)
c.create_text(45, y, anchor='e', text='%d'% (20*i))
#create scatter plots from random x-y values
for i in range(35):
    x,y = random.randint(100,210), random.randint(50,250)
    c.create_oval(x-3, y-3, x+3, y+3, width=1, fill='red')
root.mainloop()
  3. Now, let's plot a sample bar graph:
    Engage Thrusters

    A bar graph can be easily generated using the Canvas widget's create_rectangle method. A sample bar graph code is provided in 7.10 bar graph.py:

    import Tkinter
import random
root = Tkinter.Tk()
cwidth = 250
cheight = 220
barWidth = 20
canv = Tkinter.Canvas(root, width=cwidth, height=cheight, bg= 'white')
canv.pack()

plotdata= [random.randint(0,200) for r in xrange(12)]

for x, y in enumerate(plotdata):
    x1 = x  + x * barWidth
    y1 = cheight - y 
    x2 = x  + x * barWidth + barWidth    
    y2 = cheight
    canv.create_rectangle(x1, y1, x2, y2, fill="blue")
    canv.create_text(x1+3, y1, text=str(y), anchor='sw')

root.mainloop()
  4. Finally, we're going to look at how to embed matplotlib graphs in Tkinter Toplevel window.

    Using Tkinter Canvas to draw graphs may work fine for trivial cases. However, Tkinter may not be the best library when it comes to drawing more sophisticated and interactive graphs.

    In fact, matplotlib is used in conjunction with the NumPy module is the preferred choice when it comes to producing professional-quality graphs with Python.

    Engage Thrusters

    Although a detailed discussion on matplotlib is beyond the scope of this book, we will take a brief look at embedding matplotlib-generated graphs on a Tkinter canvas.

    Tip

    If you are interested in exploring advanced graphing with Python, you can install matplotlib and NumPy (a dependency for matplotlib) with the help of the installation instructions available at http://matplotlib.org/users/installing.html 

    import Tkinter as Tk
from numpy import arange, sin, pi
from matplotlib.backends.backend_tkagg import FigureCanvasTkAgg, NavigationToolbar2TkAgg
from matplotlib.figure import Figure
root = Tk.Tk()
#creating the graph
f = Figure(figsize=(5,4), dpi=100)
a = f.add_subplot(111)
t = arange(-1.0,1.0,0.001)
s = t*sin(1/t)
a.plot(t,s)
# embedding matplotlib figure 'f' on a tk.DrawingArea
canvas = FigureCanvasTkAgg(f, master=root)
canvas.get_tk_widget().pack(side=Tk.TOP, fill=Tk.BOTH, expand=1)
#creating toolbar
toolbar = NavigationToolbar2TkAgg( canvas, root )
toolbar.update()
root.mainloop()

Objective Complete – Mini Debriefing

This completes our brief discussion on the graphing abilities of Tkinter.

In this iteration, we saw how to use Tkinter Canvas to draw basic graphs such as pie chart, scatter plots, and bar graphs.

We also saw how to embed more sophisticated matplotlib graphs, on the Tkinter drawing area.

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