codeforms 0.2.0

Python library for creating, validating, and rendering web forms using Pydantic

codeforms

A Python library for dynamically creating, validating, and rendering web forms using Pydantic.

Installation

pip install codeforms

Or with uv:

uv add codeforms

Requires Python 3.9+.

Quick Start

Creating a Form

Everything starts with the Form class. A form is defined with a name and a list of fields.

from codeforms import Form, TextField, EmailField, NumberField

form = Form(
    name="UserRegistration",
    fields=[
        TextField(name="full_name", label="Full Name", required=True),
        EmailField(name="email", label="Email", required=True),
        NumberField(name="age", label="Age"),
    ]
)

The Form Class

The Form class is the main container for your form structure.

• id — Auto-generated UUID.
• name — Form name (used in HTML export and validation).
• fields — A list of field objects (e.g. TextField, EmailField).
• css_classes — Optional CSS classes for the <form> tag.
• version — Form version number.
• attributes — Dictionary of additional HTML attributes for the <form> tag.

Field Types

All fields inherit from FormFieldBase and share these common attributes:

• name — Field name (maps to name in HTML).
• label — User-visible label.
• field_type — Field type (FieldType enum).
• required — Whether the field is mandatory.
• placeholder — Placeholder text inside the field.
• default_value — Default value.
• help_text — Help text displayed below the field.
• css_classes — CSS classes for the field element.
• readonly — Whether the field is read-only.
• attributes — Additional HTML attributes for the <input> tag.

Available Fields

• TextField — Generic text input (<input type="text">).
  • minlength, maxlength: Min/max text length.
  • pattern: Regex pattern for validation.
• EmailField — Email address (<input type="email">).
• NumberField — Numeric value (<input type="number">).
  • min_value, max_value: Allowed value range.
  • step: Increment step.
• DateField — Date picker (<input type="date">).
  • min_date, max_date: Allowed date range.
• SelectField — Dropdown select (<select>).
  • options: List of SelectOption(value="...", label="...").
  • multiple: Enables multi-select.
  • min_selected, max_selected: Selection count limits (multi-select only).
• RadioField — Radio buttons (<input type="radio">).
  • options: List of SelectOption.
  • inline: Display options inline.
• CheckboxField — Single checkbox (<input type="checkbox">).
• CheckboxGroupField — Group of checkboxes.
  • options: List of SelectOption.
  • inline: Display options inline.
• FileField — File upload (<input type="file">).
  • accept: Accepted file types (e.g. "image/*,.pdf").
  • multiple: Allow multiple file uploads.
• HiddenField — Hidden field (<input type="hidden">).

Data Validation

codeforms offers multiple ways to validate user-submitted data, leveraging Pydantic's validation engine.

Recommended: FormDataValidator

The most robust approach is FormDataValidator.create_model, which dynamically generates a Pydantic model from your form definition. This gives you powerful validations and detailed error messages automatically.

from codeforms import Form, FormDataValidator, TextField, SelectField, SelectOption
from pydantic import ValidationError

# 1. Define your form
form = Form(
    name="MyForm",
    fields=[
        TextField(name="name", label="Name", required=True),
        SelectField(
            name="country",
            label="Country",
            options=[
                SelectOption(value="us", label="United States"),
                SelectOption(value="uk", label="United Kingdom"),
            ]
        )
    ]
)

# 2. Create the validation model
ValidationModel = FormDataValidator.create_model(form)

# 3. Validate incoming data
user_data = {"name": "John", "country": "us"}

try:
    validated = ValidationModel.model_validate(user_data)
    print("Valid!", validated)
except ValidationError as e:
    print("Validation errors:", e.errors())

This approach integrates seamlessly with API backends like FastAPI or Flask, since it produces standard Pydantic models.

Other Validation Methods

Two simpler alternatives exist, though FormDataValidator is preferred:

1. form.validate_data(data) — Built-in method on the Form class. Less flexible; doesn't produce Pydantic models.
2. validate_form_data(form, data) — Standalone function with basic validation logic.

Exporting Forms

Once your form is defined, you can export it to different formats.

# Export to plain HTML
html_output = form.export('html', submit=True)
print(html_output['output'])

# Export to HTML with Bootstrap 5 classes
bootstrap_output = form.export('html_bootstrap5', submit=True)
print(bootstrap_output['output'])

# Export to JSON
json_output = form.to_json()
print(json_output)

# Export to a Python dictionary
dict_output = form.to_dict()
print(dict_output)

Supported Formats

Format	Description
html	Semantic HTML
html_bootstrap4	HTML with Bootstrap 4 classes
html_bootstrap5	HTML with Bootstrap 5 classes
json	JSON representation of the form
dict	Python dictionary representation

HTML export can also generate a <script> block for basic client-side validation.

Internationalization (i18n)

All validation and export messages are locale-aware. English (en) and Spanish (es) are included out of the box, and you can register any additional language at runtime via register_locale().

Switching Locales

from codeforms import set_locale, get_locale, get_available_locales

print(get_locale())            # "en"
print(get_available_locales()) # ["en", "es"]

set_locale("es")
# All validation messages will now be in Spanish

Registering a Custom Locale

You can add any locale at runtime. Missing keys automatically fall back to English.

from codeforms import register_locale, set_locale

register_locale("pt", {
    "field.required": "Este campo é obrigatório",
    "field.required_named": "O campo {name} é obrigatório",
    "email.invalid": "E-mail inválido",
    "number.min_value": "O valor deve ser maior ou igual a {min}",
    "form.validation_success": "Dados validados com sucesso",
    "form.data_validation_error": "Erro na validação dos dados",
})

set_locale("pt")

Using the Translation Function

The t() function translates a message key, with optional interpolation:

from codeforms import t, set_locale

set_locale("en")
print(t("field.required"))                     # "This field is required"
print(t("field.required_named", name="email")) # "The field email is required"

set_locale("es")
print(t("field.required"))                     # "Este campo es requerido"
print(t("text.minlength", min=3))              # "La longitud mínima es 3"

Locale-Aware Validation

All validation functions respect the active locale:

from codeforms import Form, TextField, validate_form_data, set_locale

form = Form(
    name="example",
    fields=[TextField(name="name", label="Name", required=True)]
)

set_locale("en")
result = validate_form_data(form, {})
print(result["errors"][0]["message"])  # "The field name is required"

set_locale("es")
result = validate_form_data(form, {})
print(result["errors"][0]["message"])  # "El campo name es requerido"

See examples/i18n_usage.py for a full working example.

Custom Field Types

You can create your own field types by subclassing FormFieldBase and registering them with register_field_type(). Custom fields integrate seamlessly with forms, JSON serialization, validation, and HTML export.

Defining a Custom Field

from codeforms import FormFieldBase, register_field_type

class PhoneField(FormFieldBase):
    field_type: str = "phone"       # unique string identifier
    country_code: str = "+1"

class RatingField(FormFieldBase):
    field_type: str = "rating"
    min_rating: int = 1
    max_rating: int = 5

register_field_type(PhoneField)
register_field_type(RatingField)

Using Custom Fields in Forms

from codeforms import Form, TextField

form = Form(
    name="feedback",
    fields=[
        TextField(name="name", label="Name", required=True),
        PhoneField(name="phone", label="Phone", country_code="+54"),
        RatingField(name="score", label="Score", max_rating=10),
    ],
)

JSON Roundtrip

Custom fields serialize and deserialize automatically (as long as the field type is registered before deserialization):

import json

json_str = form.to_json()
restored = Form.loads(json_str)

assert isinstance(restored.fields[1], PhoneField)
assert restored.fields[1].country_code == "+54"

Listing Registered Types

from codeforms import get_registered_field_types

for name, classes in sorted(get_registered_field_types().items()):
    print(f"{name}: {[c.__name__ for c in classes]}")

See examples/custom_fields.py for a full working example.

License

MIT