官术网_书友最值得收藏!

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).

主站蜘蛛池模板: 黎城县| 望城县| 文化| 梁平县| 南部县| 巴里| 德格县| 平果县| 虎林市| 唐海县| 晋城| 博罗县| 泊头市| 黄龙县| 云霄县| 剑阁县| 桃源县| 繁峙县| 博兴县| 乃东县| 万荣县| 沿河| 武邑县| 文水县| 澎湖县| 青海省| 麟游县| 新龙县| 九龙坡区| 府谷县| 淳化县| 亳州市| 城固县| 江西省| 镇坪县| 双城市| 宜兰县| 南通市| 南陵县| 蕉岭县| 东方市|