from __future__ import print_function
try:
    import Tkinter
except ImportError:
    import tkinter as Tkinter

# This time, we alter the pattern very slightly by moving
# the import statements inside the function body.  This
# is marginally better in that (a) if this module was
# imported but not used, Tkinter and Canvas would not
# be imported; and (b) references to Tkinter and Canvas
# in the functions are a hair faster than if we imported
# at the module level.
def main():
	app = Tkinter.Frame()
	app.grid(sticky="nsew")

	# We have to tell the toplevel window that the frame
	# that we created should be adjustable (weight != 0)
	top = app.winfo_toplevel()
	top.columnconfigure(0, weight=1)
	top.rowconfigure(0, weight=1)

	make_ui(app)
	app.mainloop()

# In this program, we create a Canvas widget in the
# main application frame and populate it with some
# graphical items.  The Canvas module defines classes
# for rectangles, ovals, lines and several other
# graphical forms.  All of them derive from the
# CanvasItem class, which provides many methods such
# as "bind" and "config" (which act similarly to
# methods of the same name in widgets) and "move"
# (which is not defined for widgets).  The first
# argument to a CanvasItem subclass is a Canvas
# instance ("c" in this case).  The second argument
# is a list of coordinates.  For rectangles, the
# coordinates are the coordinates of two opposite
# corners; for ovals, they are the coordinates of
# the opposite corners of the smallest rectangle
# containing the oval; for lines, the list are the
# coordinates for consecutive vertices in the lines.
# All other arguments are keyword arguments.  The
# most commonly used is "fill" which defines the
# color of the item.
def make_ui(app):
	c = Tkinter.Canvas(app, width=400, height=400, bg="cyan")
	# Just as above, we need to tell "app" that the widget
	# in row 0, column 0 is resizable
	app.columnconfigure(0, weight=1)
	app.rowconfigure(0, weight=1)
	c.grid(row=0, column=0, sticky="nsew")
	r = c.create_rectangle((10, 10, 20, 30), fill="green")
	r2 = c.create_oval((300, 200, 100, 100), fill="blue")
	l = c.create_line((20, 30, 200, 100), fill="red")

if __name__ == "__main__":
	main()
	print("Finished")