Python lambda is not Getting Variables From Function

Question

I want to get which button was clicked within for loop but i can't able to get button inside the function and the button is generated by for loop and code is this:

from tkinter import * 
from tkinter import ttk

class Application(Tk):
    
    def __init__(self):
        super(Application, self).__init__()
        self.create_grid()

    def create_grid(self):
        for i in range(1, 4):
            self.btn= ttk.Button(self, text="", command=lambda btn=self.btn: self.clik(btn))
            self.btn.grid(ipadx=20, ipady=20, row=i, column=0)


    def clik(self, btn):
        print(btn)


if __name__ == '__main__':
    app = Application()
    app.mainloop()

Error:

    self.btn= ttk.Button(self, text="", command=lambda btn=self.btn: self.clik(btn))
  File "fakepath\__init__.py", line 2346, in __getattr__
    return getattr(self.tk, attr)
AttributeError: '_tkinter.tkapp' object has no attribute 'btn'

Thanks For Any Help.

command in separate line self.btn.configure(command=lambda btn=self.btn: self.clik(btn)) — Art
– Art, Commented Jun 10, 2021 at 7:36
You could also from functools import partial and then self.btn.config(command=partial(self.click, self.btn)) (obviously place the import at the beginning of the code) — Matiiss
– Matiiss, Commented Jun 10, 2021 at 7:41
As far as I understand it just returns a function with the given arguments so that it will run with those arguments every time, basically the same as with the lambda function just shorter and probably has other uses — Matiiss
– Matiiss, Commented Jun 10, 2021 at 7:54

Delrius Euphoria · Accepted Answer · 2021-06-10 08:10:59Z

2

In python, the RHS of an assignment is first evaluated and then it stores the value in LHS or so. Here if you notice:

self.btn= ttk.Button(self, text="", command=lambda btn=self.btn: self.clik(btn))

self.btn is only defined after the RHS of this line is evaluated, but inside this line itself you are referencing to the self.btn, which is not defined(yet). Hence the error of not having an attribute btn. So what you can do is assign the command in the next line:

self.btn = ttk.Button(self, text="")
self.btn['command'] = lambda btn=self.btn: self.clik(btn)

edited Jun 10, 2021 at 8:10

answered Jun 10, 2021 at 8:05

Delrius Euphoria

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3 Comments

TangerCity Over a year ago

can you join disuccsion?

Delrius Euphoria Over a year ago

@TangerCity I do not have the link, you should tag me in it.

TangerCity Over a year ago

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