textual-wtf 0.1.2

Declarative forms library for Textual TUI applications

textual-wtf

Declarative, validated forms for Textual TUI applications.

Write a Python class; get a fully-featured form — rendered, validated, and data-bound — with no boilerplate.

📖 Full documentation, guides and API reference: holdenweb.com/textual-wtf

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Installation

pip install textual-wtf

Try the demo

uvx textual-wtf                  # before installation
textual-wtf                      # if installed in an active venv
python -m textual_wtf.examples   # from a source checkout

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Quick start

Define a form class, call .layout() to render it, and handle the Submitted message:

from textual.app import App, ComposeResult
from textual_wtf import Form, StringField, IntegerField, BooleanField
from textual_wtf.forms import BaseForm


class ContactForm(Form):
    name       = StringField("Name",  required=True, max_length=80)
    age        = IntegerField("Age",  min_value=0, max_value=150)
    newsletter = BooleanField("Subscribe to newsletter")


class MyApp(App):
    def compose(self) -> ComposeResult:
        self.form = ContactForm()
        yield self.form.layout()

    # Handler name comes from BaseForm.Submitted — Form inherits it unchanged.
    def on_base_form_submitted(self, event: BaseForm.Submitted) -> None:
        data = event.form.get_data()   # {"name": "…", "age": 42, "newsletter": False}
        self.notify(f"Received: {data}")

    def on_base_form_cancelled(self, event: BaseForm.Cancelled) -> None:
        self.exit()


if __name__ == "__main__":
    MyApp().run()

Enter submits; Escape cancels. Validation runs automatically: required fields and range/length constraints are checked on blur and on submit, and any field with an error displays its message directly beneath the input.

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Field types

Class	Textual widget	Key kwargs
StringField	Input	required, min_length, max_length
IntegerField	Input (digits only)	required, min_value, max_value
BooleanField	Checkbox	—
ChoiceField	Select	choices
TextField	TextArea	max_length

All fields accept help_text= and a validators= list. Extra keyword arguments are forwarded directly to the underlying Textual widget — for example StringField("Password", password=True) gives you a masked input.

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Label and help-text styles

Control where labels and help text appear at form-class, form-instance, field, or per-render-call level:

class CompactForm(Form):
    label_style = "placeholder"   # "above" (default) | "beside" | "placeholder"
    help_style  = "tooltip"       # "below" (default) | "tooltip"

    username = StringField("Username", help_text="3–30 characters")
    email    = StringField("Email",    help_text="Used for notifications")

"placeholder" folds the label into the Input placeholder — saving a full row per text field. "tooltip" moves help text off the screen and onto a hover tooltip.

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Embedded sub-forms

Assign a Form instance as a class attribute and its fields are flattened into the parent with a prefix:

class AddressForm(Form):
    street = StringField("Street", required=True)
    city   = StringField("City",   required=True)


class OrderForm(Form):
    billing  = AddressForm()
    shipping = AddressForm(required=False)
    notes    = TextField("Notes")

Fields become billing_street, billing_city, shipping_street, … and get_data() / set_data() work on the merged flat namespace.

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Cross-field validation

Override clean_form() for validation that spans more than one field:

class PasswordChangeForm(Form):
    current = StringField("Current password", required=True, password=True)
    new     = StringField("New password",     required=True, password=True)
    confirm = StringField("Confirm",          required=True, password=True)

    def clean_form(self) -> bool:
        if self.new.value == self.current.value:
            self.add_error("new", "New password must differ from current")
            return False
        if self.new.value != self.confirm.value:
            self.add_error("confirm", "Passwords do not match")
            return False
        return True

add_error(field_name, message) attaches the error to the named field and marks it visible in the UI.

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Multi-tab forms

from textual_wtf import TabbedForm

class SettingsScreen(Screen):
    def compose(self) -> ComposeResult:
        yield TabbedForm(ProfileForm(), PreferencesForm(), AccessibilityForm())

Tab labels turn red when a tab contains a validation error, guiding the user to the problem without them having to click through every tab.

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Custom layouts

Subclass ControllerAwareLayout and override compose(). Access the current form as self.form; use bf.simple_layout() for the full label + input + error chrome, or call bf() for the raw Textual widget alone:

from textual.containers import Horizontal
from textual.widgets import Button
from textual_wtf import ControllerAwareLayout


class TwoColumnLayout(ControllerAwareLayout):
    def compose(self):
        with Horizontal():
            yield self.form.first_name.simple_layout()
            yield self.form.last_name.simple_layout()
        yield self.form.email.simple_layout()
        with Horizontal(id="buttons"):
            yield Button("Submit", id="submit", variant="primary")
            yield Button("Cancel", id="cancel")

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Custom validators

Subclass Validator and raise ValidationError when the value is invalid:

from textual_wtf.validators import Validator, ValidationError


class StrongPassword(Validator):
    def validate(self, value: str) -> None:
        if not any(c.isdigit() for c in value):
            raise ValidationError("Must contain at least one digit")
        if not any(c.isupper() for c in value):
            raise ValidationError("Must contain at least one uppercase letter")


class SignupForm(Form):
    password = StringField("Password", required=True,
                           validators=[StrongPassword()])

Plain functions also work — wrap them in validators=[my_function] and they are promoted to FunctionValidator automatically.

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Development setup

git clone https://github.com/holdenweb/textual-wtf
cd textual-wtf
uv sync
uv run pytest

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📖 Guides · API reference · how-to recipes: holdenweb.com/textual-wtf