- Tkinter GUI Application Development Blueprints(Second Edition)
- Bhaskar Chaudhary
- 234字
- 2021-06-24 18:35:04
Command binding
The simplest way to add functionality to a button is called command binding, whereby a callback function is mentioned in the form of command = some_callback in the widget option. Note that the command option is available only for a few selected widgets.
Take a look at the following sample code:
def my_callback ():
# do something when button is clicked
After defining the preceding callback, we can connect it to, say, a button with the command option referring to the callback, as follows:
tk.Button(root, text="Click me", command=my_callback)
A callback is a function memory reference ( my_callback in the preceding example) that is called by another function (which is Button in the preceding example) and that takes the first function as a parameter. Put simply, a callback is a function that you provide to another function so that it can calling it.
Note that my_callback is passed without parentheses, (), from within the widget command option, because when the callback functions are set it is necessary to pass a reference to a function rather than actually call it.
If you add parentheses, (), as you would for any normal function, it would be called as soon as the program runs. In contrast, the callback is called only when an event occurs (the pressing of a button in this case).
- Oracle 11g從入門到精通(第2版) (軟件開發(fā)視頻大講堂)
- Java 開發(fā)從入門到精通(第2版)
- R語言經典實例(原書第2版)
- Java應用開發(fā)與實踐
- PHP網絡編程學習筆記
- 前端架構:從入門到微前端
- Windows Server 2012 Unified Remote Access Planning and Deployment
- 軟件工程
- Flutter跨平臺開發(fā)入門與實戰(zhàn)
- HTML5與CSS3基礎教程(第8版)
- 批調度與網絡問題的組合算法
- Java面向對象程序設計
- Java語言程序設計教程
- 一本書講透Java線程:原理與實踐
- Access 2010數(shù)據(jù)庫應用技術實驗指導與習題選解(第2版)