Python GUI Programming Cookbook, Second Edition - Second Edition

How it works...

In line 24, we get the value of the Entry widget. We have not used OOP yet, so how come we can access the value of a variable that was not even declared yet?

Without using OOP classes, in Python procedural coding, we have to physically place a name above a statement that tries to use that name. So how come this works (it does)?

The answer is that the button click event is a callback function, and by the time the button is clicked by a user, the variables referenced in this function are known and do exist.

Life is good.

Line 27 gives our label a more meaningful name; for now, it describes the text box below it. We moved the button down next to the label to visually associate the two. We are still using the grid layout manager, ...