# Segmented

> A group of mutually exclusive text buttons. A native Pyzed component for Python desktop GUIs, with a live preview, code examples and its API.

Source: https://albakore.github.io/pyzed/library/segmented/

:::tip[In plain words]
A row of joined buttons where exactly one is chosen, like Day / Week / Month in a calendar.
:::

A row of joined buttons where one is selected. `on_select` receives the chosen option.

`ui.segmented` · Category: [Forms](https://albakore.github.io/pyzed/library/#forms) · [Full reference →](https://albakore.github.io/pyzed/reference/ui/#segmented)

**Code:**

```python
pz.column([
    ui.segmented(["Editor", "Terminal", "Both"], "Editor", on_select),
    ui.segmented(["Day", "Week", "Month"], "Week", on_select),
], spacing=14, align="center")
```

## When to use

- To switch between two to five views or modes (Day / Week / Month).
- For icons only, use a [Toggle group](https://albakore.github.io/pyzed/library/toggle-group/).

## Usage

```python
import pyzed as pz
from pyzed import ui

class Calendar(pz.App):
    def __init__(self):
        self.mode = "Week"

    def view(self):
        return ui.segmented(["Day", "Week", "Month"], self.mode, lambda m: setattr(self, "mode", m))
```

## Variants

:::note[About these captures]
Each capture is recorded by pyzed itself, off-screen at 2x, in One Dark or One Light to match this site's theme, and cropped to the component so it shows at its real size. The pointer hovers, presses or types into it; a component that does not react to the pointer cycles through a few themes. With reduced motion you see the first frame. Open **Code** under a capture to see the snippet that draws it; free names such as `on_save` stand for your own callbacks.
:::

### Options

```python
ui.segmented(["Code", "Preview"], "Code", on_select)
```

```python
ui.segmented(["Day", "Week", "Month"], "Week", on_select)
```

```python
ui.segmented(["XS", "S", "M", "L", "XL"], "M", on_select)
```

### Selection

```python
ui.segmented(["Editor", "Terminal", "Both"], "Editor", on_select)
```

```python
ui.segmented(["Editor", "Terminal", "Both"], "Both", on_select)
```

### States and events

```python
ui.segmented([("list", "List", "list"), ("grid", "Grid", "layout-grid")], "grid", on_select)
```

```python
ui.segmented(["Day", "Week", "Month"], "Week", on_select, width=320)
```

```python
ui.segmented(["Day", "Week", "Month"], "Day", on_select, disabled={"Month"})
```

```python
ui.segmented(["Code", "Preview"], "Code", on_select, size="sm")
```

## Events

Segmented has **1 event of its own**, listed below. Like every widget it also has the **18 common events** (`click`, `double_click`, `right_click`, `mouse_enter`, `drag`, `key_down`, `resize`…), attached with `.on(...)`: see [Events](https://albakore.github.io/pyzed/guides/events/) and [Events of every component](https://albakore.github.io/pyzed/library/events/).

| Event | Handler gets | When |
| --- | --- | --- |
| `on_select` | `(item)` | Callable that receives the chosen item. |

**Handler gets** is what Pyzed passes to your callable: `()` means nothing. Any handler can also be a message (a value that is not callable), which goes to `update()`.

### Handling the events

The same events written three ways. **Imperative**: methods of the app change `self`. **Declarative**: the handlers produce messages and one `update()` decides. **Functional**: a pure function draws an immutable state and asks for changes with `set_state(...)`. See [Imperative, declarative and functional](https://albakore.github.io/pyzed/guides/code-styles/).

**Imperative:**

```python
class Calendar(pz.App):
    def __init__(self):
        self.mode = "Week"

    def view(self):
        return pz.column([
            ui.segmented(["Day", "Week", "Month"], self.mode, lambda m: setattr(self, "mode", m)),
            ui.label(f"Showing a {self.mode.lower()}"),
        ], spacing=8, align="center")
```

**Declarative:**

```python
from dataclasses import dataclass

@dataclass
class Mode:
    name: str

class Calendar(pz.App):
    mode = "Week"

    def update(self, message):
        match message:
            case Mode(name):
                self.mode = name

    def view(self):
        return ui.segmented(["Day", "Week", "Month"], self.mode, Mode)
```

**Functional:**

```python
from dataclasses import dataclass

@dataclass(frozen=True)
class State:
    mode: str = "Week"

def view(state, set_state):
    return ui.segmented(["Day", "Week", "Month"], state.mode, lambda m: set_state(mode=m))
```

## Tips

:::tip
Once clicked or reached with Tab it has the keyboard focus: ←/→ pick the previous or next option (skipping disabled ones) and Home/End the first and last.
:::

## Properties and API

### `ui.segmented`

```python
segmented(
    options,
    selected,
    on_select=None,
    *,
    size='md',
    width=None,
    disabled=False,
    id=None,
    theme=None,
)
```

A group of mutually exclusive buttons.

| Property | Default | Description |
| --- | --- | --- |
| `options` | *required* | Strings, `(value, label)` or `(value, label, icon)`. |
| `selected` | *required* | The active value. |
| `size` | `"md"` | `"sm"`, `"md"` or `"lg"`. |
| `width` | `None` | `"fill"` stretches the buttons evenly. |
| `disabled` | `False` | `True`, or the values to disable. |
| `id` | `None` | Stable identifier used to focus or scroll it with a `Command`. |
| `theme` | `None` | Theme to use instead of the current one (`pyzed.theme.current()`). |

Events: `on_select` ([events](#events)).

[Full reference →](https://albakore.github.io/pyzed/reference/ui/#segmented)

## Related

- [Toggle group](https://albakore.github.io/pyzed/library/toggle-group/): An icon-only segmented control.
- [Radio group](https://albakore.github.io/pyzed/library/radio-group/): Mutually exclusive options as radio buttons.
- [Tab bar](https://albakore.github.io/pyzed/library/tab-bar/): Editor tabs with icons, dirty dots and close buttons.