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Tkinter GUI Application Development Blueprints - Second Edition by Bhaskar Chaudhary

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Passing arguments to callbacks

If a callback does not take any argument, it can be handled with a simple function, such as the one shown in the preceding code. However, if a callback needs to take arguments, we can use the lambda function, as shown in the following code snippet:

def my_callback (argument)   #do something with argument

Then, somewhere else in the code, we define a button with a command callback that takes some arguments, as follows:

tk.Button(root,text="Click", command=lambda: my_callback ('some argument'))

Python borrows a specific syntax from functional programming, called the lambda function.  The lambda function lets you define a single-line, nameless function on the fly. 

The format for using lambda is as follows:

lambda ...

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