Keypress Input
Terry Reedy
tjreedy at udel.edu
Thu Jul 16 02:08:53 EDT 2015
On 7/15/2015 9:03 PM, Rick Johnson wrote:
> You may have solved your input capturing problem, and i
> don't think a GUI is the preferred solution for a
> graphically deficient device anyhow, but you may well need a
> GUI in the future, and this would be a fine example from which
> to learn.
This really is a nice example. Your rationale for defining an app class
is the best I remember seeing.
To run in 3.x, change the first two lines to
import tkinter as tk
from tkinter.messagebox import showinfo, showerror
> import Tkinter as tk
> from tkMessageBox import showinfo, showerror
>
> MSG1 = """\
> To begin retinal stimulation, press r or g or b on your keyboard
> Hold key down for extended stimulation!
> """
>
> class App(tk.Tk):
> def __init__(self):
> tk.Tk.__init__(self)
> self.bind("<KeyPress>", self.evtKeyDown)
> self.bind("<KeyRelease>", self.evtKeyUp)
> self.protocol("WM_DELETE_WINDOW", self.evtDeleteWindow)
> w = tk.Label(self, text=MSG1)
> w.pack()
> self.config(bg='white')
> self.geometry('500x500')
> self.focus_set()
>
> def evtDeleteWindow(self):
> showinfo("The window is Dying", "Goodbye cruel world!", parent=self)
> self.destroy()
>
> def evtKeyDown(self, event):
> key = event.keysym.lower()
> alert = False
> if key == 'r':
> self.config(bg='red')
> elif key == 'g':
> self.config(bg='green')
> elif key == 'b':
> self.config(bg='blue')
> else:
Can condense block above to this easily extended code: (Replacing if
if/elif/elif/... chains, when possible, is part of mastering Python.)
try:
self['bg'] = {'r':'red', 'g':'green', 'b':'blue'}[key]
except KeyError:
> msg = 'I *TOLD* you to press r or g or b, not {0!r}!'.format(key)
> showerror('', msg, parent=self)
>
> def evtKeyUp(self, event):
> self.config(bg='white')
>
> if __name__ == '__main__':
> app = App()
> app.title('Retina Stimultor')
> app.mainloop()
> print "This code only executes *AFTER* the mainloop call returns!"
Adding parens to print, when there is a single object being printed, has
no effect in 2.x and makes the statement work in 3.x. The following
works the same in both.
print("Mainloop has returned")
--
Terry Jan Reedy
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