TypeError: takes exactly 1 argument (2 given)

Question

I'm new to programming, learnt python syntax. Stuck at my first GUI program!

Here is my code:

#User name

userLabel = Label(self.signView, text="User Name")
userLabel.grid(sticky = E)
self.userEntry = Entry(self.signView)
self.userEntry.grid(row=0, column=1)

self.labelUserVar = StringVar()
self.validLabel = Label(self.signView, textvariable=self.labelUserVar, 
                         anchor="w", fg="red")
self.validLabel.grid(row=0, column=2)
self.userEntry.bind("<Return>", self.CheckUser)

Here's the following CheckUser() function:

def CheckUser(self):
    self.labelUserVar.set("unavailable user name!")

I got this error.

TypeError: CheckUser() takes exactly 1 argument (2 given)

Answer 1

The function you pass to .bind() takes the event as an argument, and it will be passed in regardless of whether you need it.

Change the function definition to

def CheckUser(self, event):
    self.labelUserVar.set("unavailable user name!")