Strings, Numbers and Booleans¶

Simple Fields¶

class Scalar(value=Unspecified, **kw)¶

Bases: flatland.schema.base.Element

The base implementation of simple values such as a string or number.

Scalar subclasses are responsible for translating the most common data types in and out of Python-native form: strings, numbers, dates, times, Boolean values, etc. Any data which can be represented by a single (name, value) pair is a likely Scalar.

Scalar subclasses have two responsibilities: provide a method to adapt a value to native Python form, and provide a method to serialize the native form to a Unicode string.

This class is abstract.

adapt(value)¶

Given any value, try to coerce it into native format.

Returns:	the native format or raises AdaptationError on failure.

This abstract method is called by set().

serialize(value)¶

Given any value, coerce it into a Unicode representation.

Returns:	Must return a Unicode object, always.

No special effort is made to coerce values not of native or a compatible type.

This semi-abstract method is called by set(). The base implementation returns unicode(value).

set(value)¶

Assign the native and Unicode value.

Returns:	True if adaptation of value was successful.

Attempts to adapt the given value and assigns this element’s value and u attributes in tandem.

If adaptation succeeds, .value will contain the adapted native Python value and .u will contain a Unicode serialized version of it. A native value of None will be represented as u'' in .u.

If adaptation fails, .value will be None and .u will contain unicode(value) or u'' for none.

validate_element(state, descending)¶

Validates on the first, downward pass.

See FieldSchema.validate_element().

Strings¶

class String(value=Unspecified, **kw)¶

Bases: flatland.schema.scalars.Scalar

A regular old Unicode string.

adapt(value)¶

Return a Unicode representation.

Returns:	a unicode value or None

If strip is true, leading and trailing whitespace will be removed.

serialize(value)¶

Return a Unicode representation.

Returns:	a unicode value or u'' if *value* is ``None

If strip is true, leading and trailing whitespace will be removed.

is_empty¶

True if the String is missing or has no value.

strip¶

If true, strip leading and trailing whitespace during conversion.

Numbers¶

class Number(value=Unspecified, **kw)¶

Bases: flatland.schema.scalars.Scalar

Base for numeric fields.

Subclasses provide type_ and format attributes for adapt() and serialize().

adapt(value)¶

Generic numeric coercion.

Returns:	an instance of type_ or None

Attempt to convert value using the class’s type_ callable.

serialize(value)¶

Generic numeric serialization.

Returns:	a unicode string formatted with format or the unicode() of value if value is not of type_

Converts value to a string using Python’s string formatting function and the format as the template. The value is provided to the format as a single, positional format argument.

format¶

The unicode serialization format.

signed¶

If true, allow negative numbers. Default True.

type_¶

The Python type for values, such as int or float.

class Integer(value=Unspecified, **kw)¶

Bases: flatland.schema.scalars.Number

Element type for Python’s int.

format¶

u'%i'

type_¶

int

class Long(value=Unspecified, **kw)¶

Bases: flatland.schema.scalars.Number

Element type for Python’s long.

format¶

u'%i'

type_¶

long

class Float(value=Unspecified, **kw)¶

Bases: flatland.schema.scalars.Number

Element type for Python’s float.

format¶

u'%f'

type_¶

float

class Decimal(value=Unspecified, **kw)¶

Bases: flatland.schema.scalars.Number

Element type for Python’s Decimal.

format¶

u'%f'

type_¶

decimal.Decimal

Booleans¶

class Boolean(value=Unspecified, **kw)¶

Bases: flatland.schema.scalars.Scalar

Element type for Python’s bool.

adapt(value)¶

Coerce value to bool.

Returns:	a bool or None

If value is a string, returns True if the value is in true_synonyms, False if in false_synonyms and None otherwise.

For non-string values, equivalent to bool(value).

serialize(value)¶

Convert bool(value) to a canonical string representation.

Returns:	either self.true or self.false.

false¶

The unicode serialization for False: u''.

false_synonyms¶

A sequence of acceptable string equivalents for False.

Defaults to (u'off', u'false', u'False', u'0', u'')

true¶

The unicode serialization for True: u'1'.

true_synonyms¶

A sequence of acceptable string equivalents for True.

Defaults to (u'on', u'true', u'True', u'1')