Keybind causes function to run automatically on startup

Question

I am trying to create a keybind for my Entry, which takes what the user has inputted into the Entry and then calls a function.

My code:

def nameValidation(name):
    if PresenceCheck(name) and LengthCheck(name,2) and DataTypeCheck(name,str):
        print("Valid Name")
    else:
        nameEntry.configure(bg="red")
nameEntry = tk.Entry(root,textvariable=nameInput,bg="white",font=("Arial",28))
nameEntry.grid(row=2,column=2)
nameEntry.bind("<FocusOut>",nameValidation(nameInput.get()))

When I run the code, the Entry is coloured red, indicating the function has been called, even though the keybind was not activated.

in the last line you're calling the function instead of referencing it as a callback — michalwa, Jun 27 '20 at 14:42

10 Rep · Accepted Answer · 2020-06-27T14:54:12.787

2

You are making a very common mistake. Your function is executing on the execution of your program, because you have called it with parentheses in your .bind().

A way to fix this would be to add a lambda.

Code:

def nameValidation(name, event = None):
    if PresenceCheck(name) and LengthCheck(name,2) and DataTypeCheck(name,str):
        print("Valid Name")
    else:
        nameEntry.configure(bg="red")
nameEntry = tk.Entry(root,textvariable=nameInput,bg="white",font=("Arial",28))
nameEntry.grid(row=2,column=2)
nameEntry.bind("<FocusOut>", lambda: nameValidation(nameInput.get()))

Hope this helps!

As stated in the comments, use lambda: event if you want the anonymous function. If you get an error with that, use lambda _:

edited Jun 27 '20 at 14:54

answered Jun 27 '20 at 14:40

10 Rep

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2

This will throw an error all the binds pass an event argument to the first parameter of the callback function. – Saad Jun 27 '20 at 14:45
@Saad Thanks for pointing out that error. I will edit my answer. – 10 Rep Jun 27 '20 at 14:46
1

Here the callback function is the anonymous function lambda not `nameValidation`, it should be `lambda event: ... ` – Saad Jun 27 '20 at 14:49
@Saad I get this error with your solution in the line def nameValidation(event = None, name): SyntaxError: non-default argument follows default argument – Lyra Orwell Jun 27 '20 at 14:50
2

or just `lambda _: ...` if you're not using the argument – michalwa Jun 27 '20 at 14:50
1

Also, `nameValidation(event = None, name)` this will give an error. You can't give a default parameter before a normal parameter – Saad Jun 27 '20 at 14:53
@Saad I am sorry! I think I am sleepy, let me edit my answer. – 10 Rep Jun 27 '20 at 14:54

Keybind causes function to run automatically on startup

1 Answers1