Questions about Entry widget in Python tkinter

Python Help
1

In this code, which works fine, I am curious. See below.

def get_entry(event):            # line 68
    freq1=start_freq.get()
    print("Start Freq: ", freq1)
    print(event)

# create start freq
Label(button_frame, text="Start Freq MHz").grid(row=7, column=6)
start_freq = tk.Entry(button_frame)
start_freq.grid(row=7, column=7)
start_freq.bind("<Return>", get_entry)
  1. I get this for the print(event). Event can be spelled any way, it was event in the example but that was confusing because it has nothing to do with event in the print. I used snow in both places with the same result. Where does it come from?
<KeyPress event send_event=True keysym=Return keycode=13 char='\r' x=22 y=5>
  1. Without the print(event) statement I get this. I don’t need the print, I was curious.

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image395×139 22.1 KB

  1. If I delete event from the function definition (def get_entry()) I get an error

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image1051×114 47.8 KB

  1. Why is get_entry in the last line not get_entry()
2

The line:

start_freq.bind("<Return>", get_entry)

tells tkinter to call the function get_entry when the Return key is pressed.

When tkinter calls that function, it passes information to the function about why it was called. That’s the event parameter. Sometimes that information is useful, but many times it’s not.

The warning is to tell you that you haven’t done anything with the parameter. That might be because you’ve made a mistake, but sometimes you just don’t care about that parameter. It doesn’t know whether it’s intentional.

Finally, you want to pass the function get_entry to bind. If you wrote get_entry(), you’d be call it and then passing the returned result to bind. What does it return? It returns None, so that’s what you’d be passing to bind.

3

Thanks Matthew, now I understand.