trafaret 0.4.7

trafaret is Python validation library with support to convert data structures. Sample of usage:

import datetime
import trafaret as t

date = t.Dict(year=t.Int, month=t.Int, day=t.Int) >> (lambda d: datetime.datetime(**d))
assert task.check({'year': 2012, 'month': 1, 'day': 12}) == datetime.datetime(2012, 1, 12)

t.Dict creates new dict structure validator with three t.Int elements. >> operation adds lambda function to the converters of given checker. Obviously every checker have any default converter, but when you use >> or .append, you disable default converter.

DataError

Exception class that used in library. Exception hold errors in error attribute. For simple checkers it will be just a string. For nested structures it will be dict instance.

Trafaret

Base class for trafarets. Use it to make new trafarets. In derrived classes you need to implement _check or _check_val methods. _check_val must return value, _check must return None on success.

You can implement converter method, if you want to convert value somehow, but want to make free for developer to apply his own converters to raw data.

Type

Just instantitate it with any class, like int, float, str::

 >>> Type(int).check(4)
 4

Any

Will match any element.

Or

Get other converters as args, and this samples are equivalent:

 >>> Or(t.Int, t.Null).check(None)
 None
 >>> (t.Int | t.Null).check(5)
 5

Null

Value must be None.

Simple checkers

Bool

Float

Int

Atom - value must be exactly equal to Atom first arg - t.Atom('this_key_must_be_this').

String

regex param - will return re.Match object. Default converter will return match.group().

Email and URL just provide regular expressions and a bit of logic for IDNA domains.

List

Just List of elements of one type. In converter you will get list instance of converted elements.

Dict

Dict include named params. You can use for keys plain strings and Key instances.

Methods:

allow_extra(*names) : where names can be key names or * to allow any additional keys.

make_optional(*names) : where names can be key names or * to make all options optional.

Key

Special class to create dict keys. Parameters are:

 name - key name
 default - default if key is not present
 optional - if True allow to not provide arg
 to_name - instead of key name will be returned this key

You can provide to_name with >> operation::
 Key('javaStyleData') >> 'plain_cool_data'

Mapping

Enum

This checker check that value one from provided. Like::

 >>> Enum(1, 2, 'error').check('2')
 2

Callable

Call

Forward

This checker is container for any checker, that you can provide later. To provide container use provide method or > node = Forward()
>> node

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Requirements:

· Python