tkinter graphics

A silly demo of tkinter

On macOS and Microsoft Windows:

python3 -m tkinter

C:\Users\Myname>py.exe -m tkinter

This is Tcl/Tk version 8.6
This should be a cedilla: ç
Click me!
QUIT

tkinter, like the other modules that we import, is a file. To find this file,

python3 -c 'import sys; import tkinter; print(sys.modules["tkinter"])'
<module 'tkinter' from '/Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/tkinter/__init__.py'>

C:\Users\Myname>py.exe -c "import sys; import tkinter; print(sys.modules['tkinter'])"
<module 'tkinter' from 'C:\\Users\\Myname\\AppData\\Local\\Programs\\Python\\Python36-32\\lib\\tkinter\\__init.py__'>

Each module can contain some extra demo code that is usually not executed when we import the module. For example, the tkinter module contains the cedilla demo we just saw. To execute the demo code, the -m option of python3 puts the string "__main__" (with a total of four underscores) into the variable __name__ in the file /Library/Frameworks/Python.framework/Versions/3.8/lib/python3.8/tkinter/__init__.py, causing the following if statement in this file to be true.

def _test():
    root = Tk()
    text = "This is Tcl/Tk version %s" % TclVersion
    text += "\nThis should be a cedilla: \xe7"
    etc.
    root.mainloop()

if __name__ == '__main__':
    _test()

Other tkinter demos

cd /Library/Frameworks/Python.framework/Versions/3.8/share/doc/python3.8/examples/Tools/demo

pwd
/Library/Frameworks/Python.framework/Versions/3.8/share/doc/python3.8/examples/Tools/demo

ls -l

cat README
This directory contains a collection of demonstration scripts for
various aspects of Python programming.

beer.py        Well-known programming example: Bottles of beer.
eiffel.py      Python advanced magic: A metaclass for Eiffel post/preconditions.
hanoi.py       Well-known programming example: Towers of Hanoi.
life.py        Curses programming: Simple game-of-life.
markov.py      Algorithms: Markov chain simulation.
mcast.py       Network programming: Send and receive UDP multicast packets.
queens.py      Well-known programming example: N-Queens problem.
redemo.py      Regular Expressions: GUI script to test regexes.
rpython.py     Network programming: Small client for remote code execution.
rpythond.py    Network programming: Small server for remote code execution.
sortvisu.py    GUI programming: Visualization of different sort algorithms.
ss1.py         GUI/Application programming: A simple spreadsheet application.
vector.py      Python basics: A vector class with demonstrating special methods.

grep tkinter *.py

python3 hanoi.py
./hanoi.py
./sortvisu.py
./ss1.py
./redemo.py

The Python script:
draw the flag pixel by pixel

See Developing tkinter applications.

tkflag.py

See Flag of the United States, the Canvas widget, the create_rectangle function, and Capture a window.

The y in line 23 goes from 0 to 259 inclusive. These values are in the first column of the following table. The values of the expression
y % (2 * stripeHeight)
in line 27 are in the second column. These values go from 0 to 39 over and over again. The ones that are less than 20 are red; the others are white. (See lines 27–30.) Note that there are seven groups of red, and six groups of white.

Draw the flag rectangle by rectangle

flag2.py

And give the flag a white background color.

Give the flag one star

flag3.py

See the function create_polygon. For space cadets only: if you’d like to fill in the blue pentagon, each vertex of the blue pentagon is radius * (1 – cos(18)tan(36)) / cos(36) from the center of the blue pentagon, where the angles are in degrees.

#Another way to pass the 11 arguments to create_polygon.
#For the asterisk, see Unpacking Argument Lists.

vertices = []   #an empty list

for i in range(5):
    vertices.append(xCenter + radius * math.cos(start + i * delta))
    vertices.append(yCenter - radius * math.sin(start + i * delta))

canvas.create_polygon(*vertices, fill = "white")

Things to try

1. Wikipedia gives us the red/green/blue numbers (under “8-bit hex”) to fine-tune the colors. To draw a blue pixel,

                   color = "#3C3B6E"   #blue: decimal 60, 59, 110
   

   To draw a white pixel,

                   color = "#FFFFFF"   #white: decimal 255, 255, 255
   

   To draw a red pixel,

                   color = "#B22234"   #red: decimal 178, 34, 52
   

   Since the # is within a quoted string, it is not a comment delimiter. The # is followed by three numbers written in hexadecimal. Each number is written as two hexadecimal digits, for a total of six hexadecimal digits. The first number is the amount of red. The second number is the amount of green. The third number is the amount of blue. Each number (written as two hexadecimal digits) is an integer in the range 0 to 255 inclusive. For example, the reddish color #B22234 has a preponderance of red: B2 represents the integer 178, 22 represents the integer 34, and 34 represents the integer 52.

   Here’s how to use IDLE to translate the three numbers 178, 34, 52 to and from hexadecimal:

   >>> f"#{178:02X}{34:02X}{52:02X}"
   '#B22234'
   
   >>> (0xB2, 0x22, 0x34)
   (178, 34, 52)
   

2. Better yet, create three variables immediately before the canvas = statement.

   #red/green/blue colors
   oldGloryRed   = "#B22234"   #decimal  60,  59, 110
   oldGloryWhite = "#FFFFFF"   #decimal 255, 255, 255
   oldGloryBlue  = "#3C3B6E"   #decimal 178,  34,  52
   

   Then use the variables like this:

                   color = oldGloryRed
   

   etc.