command is performed without pressing button

Question

I have problem with performed command by pressing button (using Tkinter).

I defined function like that:

refPt = []
cropping = False

def main(image_dir):
    def click_and_crop(event, x, y, flags, param):
       global refPt, cropping


    if event == cv2.EVENT_LBUTTONDOWN:
        refPt = [(x, y)]
        cropping = True


    elif event == cv2.EVENT_LBUTTONUP:

        refPt.append((x, y))
        cropping = False


        cv2.rectangle(image, refPt[0], refPt[1], (0, 255, 0), 2)
        cv2.imshow("image", image)

image=cv2.imread(image_dir)
print (image.dtype)
clone = image.copy()
cv2.namedWindow("image")
cv2.setMouseCallback("image", click_and_crop) 

while True:

    cv2.imshow("image", image)
    key = cv2.waitKey(1) & 0xFF


    if key == ord("r"):
        image = clone.copy()


    elif key == ord("c"):
        break


if len(refPt) == 2:
    roi = clone[refPt[0][1]:refPt[1][1], refPt[0][0]:refPt[1][0]]
    cv2.imshow("ROI", roi)
    cv2.waitKey(0)
    cv2.imwrite('template.tif',roi)

cv2.destroyAllWindows()

It works fine, when i tested it alone.

This is small part of my GUI code:

window = tkinter.Tk() window.title("Analog2Digital Transform") 
b2 =    tkinter.Button(window, text="Start", command=main('7_7026_polowa.tif'),   width=10, heigh=10)

Now, when i run my script function main()is performed before showing GUI window. Additionally, it used argument of function - main('7_7026_polowa.tif'), which is included in GUI code. Is it problem with function definition or GUI code?

try renaming main to something else, your ide might be running it (main is usually executed when running a script) — Bahrom, Mar 23 '16 at 00:26

score 2 · Accepted Answer · answered Mar 23 '16 at 02:49

If you want to bind a function to a widget with the command parameter then you can't have the parenthesis.

command = main

Because with them it calls the functions instead. If you want to bind the function and pass in a value then you should look towards lambda

command = lambda : main('7_7026_polowa.tif')

If you are binding the function to a widget using the bind method instead of the command parameter then you need lambda to take the event object.

mywidget.bind("<ButtonRelease-1>", lambda e : function(e, value) )

OR if you are not using the event object then no need to pass it into the funciton.

mywidget.bind("<ButtonRelease-1>", lambda e : function(value) )

score 0 · Answer 2 · 2016-03-23T01:57:19.220

b2 =tkinter.Button(window, text="Start", command=main('7_7026_polowa.tif'),   width=10, heigh=10)

main is executed when the button is created because of the parens "()", and command=the return value. Also height is misspelled. Use partial to pass a value to a function, and command=function --> no parens when you want to call a function without passing a value.

from functools import partial
...
b2=tkinter.Button(window, text="Start", command=partial(main, '7_7026_polowa.tif'),
                  width=10, height=10)

command is performed without pressing button

2 Answers2