# CheckBox

```python
__init__(
    self,
    master,
    text="",
    command=None,
    grid=None,
    align=None,
    args=None,
    visible=True,
    enabled=None,
    width=None,
    height=None)
```

### What is it?
The `CheckBox` object displays a check box to allow an option to be ticked or un-ticked.

![Checkbox on Windows](images/checkbox_windows.png)

### How do I make one?

Create a `CheckBox` object like this:

```python
from guizero import App, CheckBox
app = App()
checkbox = CheckBox(app, text="Add extra glitter")
app.display()
```

### Starting parameters

When you create a `CheckBox` object you **must** specify `master` and `text` and you can specify any of the optional parameters. Specify parameters in the brackets, like this: `checkbox = CheckBox(app, text="Add extra glitter")`

| Parameter | Takes              | Default | Compulsory | Description                                                                                                          |
|-----------|--------------------|---------|------------|----------------------------------------------------------------------------------------------------------------------|
| master    | App, Window or Box | -       | Yes        | The container to which this widget belongs                                                                           |
| text      | string             | ""      | No         | The text to display next to the check box                                                                            |
| align     | string             | None    | -          | Alignment of this widget within its container. Possible values: `"top"`, `"bottom"`, `"left"`, `"right"`.            |
| command   | function name      | None    | -          | The name of a function to call when this checkbox is ticked/unticked                                                 |
| args      | list               | None    | -          | If you wish to pass any arguments to the function specified in the command parameter, you can specify them as a list |
| grid      | List [int, int]    | None    | -          | `[x,y]` coordinates of this widget. This parameter is only required if the `master` object has a grid layout.        |
| visible   | boolean            | True    | No         | If the widget should be visible.                                                                                     |
| enabled   | boolean            | None    | No         | If the widget should be enabled. If `None` (the default) the enabled property will be inherited from the master      |
| width     | [size](size.md)    | None    | No         | Set the width of the widget in characters or to `"fill"`                                                             |
| height    | [size](size.md)    | None    | No         | Set the height of the widget in characters or to `"fill"`                                                            |


### Methods

You can call the following methods on a `CheckBox` object.

| Method                              | Takes                                                                                | Returns | Description                                                                                                                                                    |
|-------------------------------------|--------------------------------------------------------------------------------------|---------|----------------------------------------------------------------------------------------------------------------------------------------------------------------|
| after(time, command, args=None)     | time (int), command (function name), args (list of arguments)                        | -       | Schedules a **single** call to `command` after `time` milliseconds. (To repeatedly call the same command, use `repeat()`)                                      |
| cancel(command)                     | command (function name)                                                              | -       | Cancels a scheduled call to `command`                                                                                                                          |
| destroy()                           | -                                                                                    | -       | Destroys the widget                                                                                                                                            |
| disable()                           | -                                                                                    | -       | Disables the widget so that it is "greyed out" and cannot be interacted with                                                                                   |
| enable()                            | -                                                                                    | -       | Enables the widget                                                                                                                                             |
| focus()                             | -                                                                                    | -       | Gives focus to the widget                                                                                                                                      |
| hide()                              | -                                                                                    | -       | Hides the widget from view. This method will unpack the widget from the layout manager.                                                                        |
| repeat(time, command, args=None)    | time (int), command (function name), args (list of arguments)                        | -       | Repeats `command` every `time` milliseconds. This is useful for scheduling a function to be regularly called, for example updating a value read from a sensor. |
| resize(width, height)               | width (int), height (int)                                                            | -       | Sets the width and height of the widget                                                                                                                        |
| show()                              | -                                                                                    | -       | Displays the widget if it was previously hidden                                                                                                                |
| toggle()                            | -                                                                                    | -       | Switches the `CheckBox` to the opposite of its current value. i.e. if it is ticked, untick it and vice versa                                                   |
| update_command(command, args =None) | command (function name), args (_Optional_ List of arguments to be passed to command) | -       | Updates the function to call when the checkbox is ticked/unticked                                                                                              |


### Properties

You can set and get the following properties:

| Method          | Data type           | Description                                                                                           |
|-----------------|---------------------|-------------------------------------------------------------------------------------------------------|
| align           | string              | The alignment of this widget within its container                                                     |
| bg              | [color](colors.md)  | The background colour of the widget                                                                   |
| enabled         | boolean             | `True` if the widget is enabled                                                                       |
| font            | string              | The font of the text                                                                                  |
| grid            | List                | `[x,y]` coordinates of this widget. This parameter is only required if the `master` object has a grid |
| height          | [size](size.md)     | Set the height of the widget in characters or to `"fill"`                                             |
| master          | App or Box          | The container to which this widget belongs                                                            |
| text            | string              | The text associated with the checkbox                                                                 |
| value           | int                 | `1` if the CheckBox is ticked or `0` if it is not ticked                                              |
| visible         | boolean             | If this widget is visible                                                                             |
| width           | [size](size.md)     | Set the width of the widget in characters or to `"fill"`                                              |
| text_size       | int                 | The size of the text                                                                                  |
| text_color      | [color](colors.md)  | The colour of the text                                                                                |
| text_bold       | boolean             | Whether the text is bold                                                                              |
| text_italic     | boolean             | Whether the text is italic                                                                            |
| text_underline  | boolean             | Whether the text is underlined                                                                        |
| text_overstrike | boolean             | Whether the text is overstruck                                                                        |
| tk              | tkinter.Checkbutton | The internal tkinter object, see [Using tkinter](usingtk.md)                                          |


Refer to a property as `<name of widget>.property`. For example, if your `CheckBox` object is called `checkbox` you would write `checkbox.value`.

You can **set** the property (for example `checkbox.value = 1`) or **get** the value of the property to use (for example `print(checkbox.value)`).

### Examples

**Creating multiple CheckBoxes**

Create multiple CheckBoxes like this.

```python
from guizero import App, CheckBox
app = App()
glitter = CheckBox(app, text="Add glitter")
sparkles = CheckBox(app, text="Add sparkles")
app.display()
```
**Calling a function when a CheckBox value changes**

You can call a function when the value of a CheckBox changes (becomes checked or unchecked). In this particular example all three CheckBoxes call the same function, but it is possible for each CheckBox object to call a different function.

```python
from guizero import App, Text, CheckBox, TextBox
def calculate_extras():
    total = 0
    if syrup.value == 1:
        total += 20
    if sprinkles.value == 1:
        total += 10
    if cream.value == 1:
        total += 50
    cost.value = total


app = App()

questions = Text(app, text="What would you like with your coffee?")

syrup = CheckBox(app, text="Caramel syrup (20p)", command=calculate_extras)
sprinkles = CheckBox(app, text="Chocolate sprinkles (10p)", command=calculate_extras)
cream = CheckBox(app, text="Whipped cream (50p)", command=calculate_extras)

cost_of_extras = Text(app, text="Cost of extras:")
cost = TextBox(app, text="0")

app.display()
```
![CheckBox calling a function](images/checkbox_function_windows.png)
