Why is the function called before pressing a button?

Question

My program draws the fractal using pointSize_max and pointSize variables, which are entered by the user in Tkinter. The problem is that the fractal is drawn before pressing a button (as soon as the program is run), and the program does not draw the fractal when the button is pressed.

pointLabel = tk.Label(frame,text="minimaalne pikkus")
pointLabel.pack()
pointSize = tk.StringVar()
pointEntry = tk.Entry(frame,textvariable=pointSize)
pointEntry.pack()
pointSize.set(str(10))

pointLabel_max = tk.Label(frame,text="maksimaalne pikkus")
pointLabel_max.pack()
pointSize_max = tk.StringVar()
pointEntry_max = tk.Entry(frame,textvariable=pointSize_max)
pointEntry_max.pack()
pointSize_max.set(str(30))

drawButton = tk.Button(frame, text = "Draw a fractal", command=koch(int(pointSize_max.get()), int(pointSize.get())))

# koch function draws the fractal 

drawButton.pack()

tk.mainloop()

Asked By: Kostya

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Source

Answer 1

The koch function is called when the button is created, as part of the parameter evaluation before the tk.Button call. You can create a function object to call instead.

def koch_invoke():
    koch(int(pointSize_max.get()), int(pointSize.get()))
drawButton = tk.Button(frame, text = "Draw a fractal", command=koch_invoke)

Answered By: Mark Ransom

Answer 2

When your script is compiled it comes to this line and runs the function since you are calling it:

command=koch(int(pointSize_max.get()), int(pointSize.get()))

Try using a lambda to prevent this from happening:

command= lambda x = int(pointSize_max.get()), y = int(pointSize.get()): koch(x, y))

Answered By: MrAlexBailey

Why is the function called before pressing a button?

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