# Combo

    __init__(
        self,
        master,
        options=[],
        selected=None,
        command=None,
        grid=None,
        align=None,
        visible=True,
        enabled=None,
        width=None,
        height=None)

### What is it?

The `Combo` object displays a drop down box allowing a single option to be selected from a list of options.

### How do I make one?

Create a `Combo` object like this:

    from guizero import App, Combo
    app = App()
    combo = Combo(app, options=["Beef", "Chicken", "Fish", "Vegetarian"])
    app.display()

### Starting parameters

When you create a `Combo` object you must specify a `master` and you can specify any of the optional parameters. Specify parameters in the brackets, like this: `combo = Combo(app, options=["Beef", "Chicken", "Fish", "Vegetarian"])`

Parameter | Takes | Default | Compulsory | Description
--- | --- | --- | --- | ---
master | App, Window or Box | - | Yes | The container to which this widget belongs
options | List | [] | No | A list of options to display
selected | string | None | No | The option to select by default
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 a different option is selected. This function MUST take either zero or one argument, if the function takes one argument the current value of the Combo will be given.
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 | None | No | Set the width of the widget in characters or to `"fill"`
height | size | None | No | Set the height of the widget in characters or to `"fill"`

### Methods

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

Method | Takes | Returns | Description
--- | --- | --- | ---
append(option) | item (string) | - | Appends a new `option` to the end of the Combo.
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`
clear() | - | - | Removes all options from the Combo box
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.
insert(index, option) | index (int), item (string) | - | Insert a new `option` in the Combo at `index`
remove(option) | item (string) | Boolean | Removes the first `option` from the Combo. Returns `True` if an item was removed.
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
select_default() | - | - | Resets the combo box so that the first item is selected
show() | - | - | Displays the widget if it was previously hidden
update_command(command) | command (function name) | - | Updates the function to call when a different option is selected.

### 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 | 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 | Set the height of the widget in characters or to `"fill"`
master | App or Box | The container to which this widget belongs
value | string | The text associated with the currently selected option
visible | boolean | If this widget is visible
width | size | Set the width of the widget in characters or to `"fill"`
text_size | int | The size of the text
text_color | color | 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.OptionMenu | The internal tkinter object, see Using tkinter

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

You can set the property (for example `combo.value = "Chicken"`) or get the value of the property to use (for example `print(combo.value)`).

### Examples

Calling a function when the value selected changes

You can call a function when the selected value in a `Combo` object changes. The function you call can take either zero or one argument, if the function takes one argument it will automatically be passed a string containing the currently selected value from the `Combo` object.

    from guizero import App, Text, Combo
    def you_chose(selected_value):
        if selected_value == "Tiny goblet":
            result.value = "You chose...wisely"
        else:
            result.value = "You chose...poorly"

    app = App()
    instructions = Text(app, text="Choose a goblet")
    combo = Combo(app, options=["", "Huge golden goblet", "Jewel encrusted goblet", "Tiny goblet"], command=you_chose)
    result = Text(app)
    app.display()