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Fields

Fields are usually declared as attributes on schema classes:

class Organisation(typesystem.Schema):
    name = typesystem.String(title="Name", max_length=100)
    date_created = typesystem.Date(title="Date created", default=datetime.date.today)
    owner = typesystem.Reference(to=User, allow_null=True)

Fields are always required in inputs, unless a default value is set.

  • Setting allow_null to True will set the default to None. (Unless default is already set.)
  • Setting allow_blank to True will set the default to "". (Unless default or allow_null is already set.)

All fields support the following arguments.

Arguments:

  • title - A string to use when labelling the input. Default: None
  • description - A string describing the input. Default: None
  • default - A value to be used if no input is provided for this field. May be a callable, such as datetime.datetime.now. Default: NO_DEFAULT
  • allow_null - A boolean determining if None values are valid. Default: False

Using fields directly

You can use fields to validate data directly, rather than using them on a schema class. This is useful if you have a general datastructure that requires validation.

For instance, we could validate a dictionary of integers, like so:

validator = typesystem.Object(properties=typesystem.Integer())
value = validator.validate(data)  # May raise `ValidationError`

Or returning a two-tuple of (value, ValidationError):

validator = typesystem.Object(properties=typesystem.Integer())
value, error = validator.validate_or_error(data)
if error:
    ...
else:
    ...

Textual data types

String

Validates single-line text inputs.

For example: username = typesystem.String(max_length=100)

Arguments:

  • allow_blank - A boolean indicating if the empty string should validate. Default: False
  • trim_whitespace - A boolean indicating if leading/trailing whitespace should be removed on validation. Default: True
  • max_length - A maximum number of characters that valid input stings may contain. Default: None
  • min_length - A minimum number of characters that valid input stings may contain. Default: None
  • pattern - A regular expression that must match. This can be either a string or a compiled regular expression. E.g. pattern="^[A-Za-z]+$" Default: None
  • format - A string used to indicate a semantic type, such as "email", "url", or "color". Default: None

Text

Validates multi-line strings. Takes the same arguments as String. Represented in HTML forms as a <textarea>.

Boolean data types

Boolean

Represented in HTML forms as a <checkbox>.

For example:

is_admin = typesystem.Boolean(default=False)

Because all fields are required unless a default is given, you'll typically want to use default=False. This is particularly true if you want to render boolean fields as HTML checkboxes, since they do not submit any input if unchecked.

Numeric data types

Number

The base class for Integer, Float, and Decimal.

You won't typically want to use this class directly, since the subclasses provide more precise behaviour.

Arguments:

  • minimum - A number representing the minimum allowed value. Inputs must be greater than or equal to this to validate. Default: None
  • maximum - A number representing the maximum allowed value. Inputs must be less than or equal to this to validate. Default: None
  • exclusive_minimum - A number representing an exclusive minimum. Inputs must be greater than this to validate. Default: None
  • exclusive_maximum - A number representing an exclusive maximum. Inputs must be less than this to validate. Default: None
  • precision - A string representing the decimal precision to truncate input with. E.g. precision="0.001". Default: None
  • multiple_of - A number giving a value that inputs must be a strict multiple of in order to validate. E.g. multiple_of=2 will only validate even integers. Default: None

Integer

Takes the same arguments as Number. Returns instances of int.

Float

Takes the same arguments as Number. Returns instances of float.

Decimal

Takes the same arguments as Number. Returns instances of decimal.Decimal.

Enumeration data types

Choice

Provides a fixed set of options to select from.

Represented in HTML forms as a <select>.

Arguments:

  • choices - A list of two-tuples of (choice, description). Default: None

Date and time data types

DateTime

Validates ISO 8601 formatted datetimes. For example "2020-02-29T12:34:56Z".

Returns datetime.datetime instances.

Date

Validates ISO 8601 formatted dates. For example "2020-02-29".

Returns datetime.date instances.

Time

Validates ISO 8601 formatted times. For example "12:34:56".

Returns datetime.time instances.

Composite data types

Array

Used to validate a list of data. For example:

# Validates data like `[8, 7, 0, 8, 4, 5]`
ratings = typesystem.Array(items=typesystem.Integer(min_value=0, max_value=10))

Arguments:

  • items - Either a Field, used to validate each item in the list. Or a list of Field instances, used to validate each item in the list, positionally. Default: None
  • additional_items - Only valid if items is a list. Either True or False, or a Field. Used to validate each additional item in the list. Default: False
  • min_items - An integer, indicating the minimum number of items that must be present in the list. Default: None
  • max_items - An integer, indicating the maximum number of items that may be present in the list. Default: None
  • exact_items - An integer, indicating the exact number of items that must be present in the list. Default: None
  • unique_items - A boolean. Used to determine if duplicate items are allowed in the list. Default: False

Object

Used to validate a dictionary of data.

# Validates data like `{"address": "12 Steeple close", "delivery note": "Leave by porch"}`
extra_metadata = typesystem.Object(properties=typesystem.String(max_length=100))

Schema classes implement their validation behaviour by generating an Object field, and automatically determining the properties and required attributes.

You'll typically want to use typesystem.Reference(to=SomeSchema) rather than using the Object field directly, but it can be useful if you have a more complex data structure that you need to validate.

Arguments:

  • properties - Either a Field, used to validate each value in the object. Or a dictionary of Field instances, used to validate each item in the list, by field name. Default: None
  • pattern_properties - A dictionary mapping regex-style strings to field instances. Used to validate any items not in properties that have a key matching the regex. Default: None
  • additional_properties - Either a boolean, used to indicate if additional properties are allowed, or a Field used to validate any items not in properties or pattern_properties. If None then additional properties are allowed, but are not included in the validated value. Default: None
  • min_properties - An integer representing the minimum number of properties that must be included.
  • max_properties - An integer representing the maximum number of properties that may be included.
  • required - A list of strings indicating any fields that are strictly required in the input.

Reference

Used to reference a nested schema.

For example:

owner = typesystem.Reference(to=User, allow_null=True)

Arguments:

  • to - A schema class or field instance. Required