============ Procrustes

Procrustes is a validation library, suitable for validating user input data, i.e. web forms or API calls. With procrustes you can validate any structure.

For doing this procrustes has three container classes - Tuple, List and Dict. Tuple come from FP, has fixed count of elements with fixed types. List can include any amount of values of one type. And Dict is a dict.

Procrustes consist of validators and forms. You can use validators without forms functionality. Forms adds mainly widgets and form data parsing.

Validators

Most simple what you can to do with procrustes is build validator and use it:

    >>> from procrustes import validators as v
    >>> two_strings_v = v.Tuple(v.String(), v.String())
    >>> auth = two_strings_v(['login', 'password'])
    >>> auth.data
    ('login', 'password')
    >>> auth.errors
    []
    >>> auth = two_strings_v(['login'])
    >>> auth.data
    >>> auth.errors
    ['Must be iterable of length 2']

We have very powerful `List`:

    >>> list_of_pairs_v = v.List(two_strings_v)
    >>> pairs = list_of_pairs_v([(str(x), str(x)) for x in xrange(10)])
    >>> pairs.data
    [('0', '0'), ('1', '1'), ('2', '2'), ('3', '3'), ('4', '4'), ('5', '5'), ('6', '6'), ('7', '7'), ('8', '8'), ('9', '9')]
    >>> pairs.errors
    []

`List`, `Tuple` and `Dict` are recursive, so you can build any data structure you want.

`Dict` example:

    >>> dict_v = v.Dict({'pair': two_strings_v, 'pairs': list_of_pairs_v})
    >>> data = dict_v({'pair': ['a', 'b'], 'pairs': [['a', 'b'], ['c', 'd']]})
    >>> data.data
    {'pair': ('a', 'b'), 'pairs': [('a', 'b'), ('c', 'd')]}
    >>> data.errors
    []

Validators have `required` keyword argument:

    >>> two_strings_v = v.Tuple(v.String(), v.String(), required=False)
    >>> dict_v = v.Dict({'pair': two_strings_v, 'pairs': list_of_pairs_v})
    >>> data = dict_v({'pairs': [['a', 'b'], ['c', 'd']]})
    >>> data.data
    {'pair': None, 'pairs': [('a', 'b'), ('c', 'd')]}
    >>> data.errors
    []

Flat
~~~~

Procrustes can `flat` data:

    >>> list(data.flatten())
    [('pairs__0__0', 'a'), ('pairs__0__1', 'b'), ('pairs__1__0', 'c'), ('pairs__1__1', 'd')]

And unflat it back:

    >>> dict_v.deepen(dict([('pairs__0__0', 'a'), ('pairs__0__1', 'b'), ('pairs__1__0', 'c'), ('pairs__1__1', 'd')]))
    {'pair': (None, None), 'pairs': [('c', 'd'), ('a', 'b')]}


Forms
~~~~~

Forms derived from validators and implemented as mixins to them. Every Field
can work as form. Your form may consist from one `forms.String()`.
In addition to validators forms adds methods `widgets`, `template_widgets`,
`unflat` and `is_valid`.