validoot - 1.3
This module is designed to solve the most basic of argument validations: types, clauses, and combinations of clauses. It is meant to remove some of the boiler plate code used to check the input types and checks such as between, or string lengths.
Github url: https://github.com/AstromechZA/validoot
Pypi url: https://pypi.python.org/pypi/validoot/1.3
Definitions
- Clause - A function that takes in the value as a parameter and
returns
True
orFalse
. - Operator - Allows you to “and” and “or” clauses together.
Basic example:
from validoot import validates, inst, typ, between
@validates(inst(basestring), typ(int), between(0, 100))
def do_something(name, id, age):
pass
In the code above, a validoot.ValidationError
will be thrown if the
name
is not a string or unicode, if the id
is not an integer, or
if the age
is not between 0 and 100.
>>> do_something('Darth Vader', 0, 42)
>>> do_something('Boba Fett', 1, 123)
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "validoot/decorators.py", line 25, in __call__
self.positional_validators[i], args[i], i))
validoot.exceptions.ValidationError: Validation <in range [0..100)> failed for value 123 ( arg[2] )
Operators:
We can extend the first example by adding an additional check for the
name
: it must be between 5 and 40 characters. For this we use the
validoot.And
operator to combine the clauses.
from validoot import validates, inst, typ, between, len_between, And
@validates(And(inst(basestring), len_between(5, 40)), typ(int), between(0, 100))
def do_something(name, id, age):
pass
An Or
operator also exists. Both And
and Or
take in a
variable number of clauses and can be nested further.
Operator shortcuts are provided for joining clauses in a different
manner which reads differently (._and(...)
, ._or(...)
). So our
previous example can be changed to look like this:
from validoot import validates, inst, typ, between, len_between
@validates(inst(basestring)._and(len_between(5, 40)), typ(int), between(0, 100))
def do_something(name, id, age):
pass
Operators can also be combined in more complicated ways:
inst(basestring)._and(len_between(5, 40))._or(typ(int))
Keyword arguments:
There is also support for keyword arguments:
from validoot import validates, inst, typ
@validates(inst(basestring), something=typ(float))
def do_something(name, something=1.0, anotherthing=2):
pass
Here the something
value must pass the validation checks as
specified in the decorator. No checks exist for anotherthing
so it
has no restrictions.
Decorating Class/Static/Instance methods or Constructors:
Methods belonging to classes can be validated as well in exactly the same way
as the examples above. Please make note of the order of the @validates
decorator and other decorators such as @classmethod
or @staticmethod
.
class SomeClass(object):
# classmethod MUST be the innermost decorator!
@validates(typ(int))
@classmethod
def some_class_method(cls, an_integer):
return an_integer
# staticmethod can be outer or inner decorator
@staticmethod
@validates(typ(float))
def some_static_method(a_floater):
return a_floater
@validates(typ(string))
def some_instance_method(self, a_string):
return a_string
In order to validate arguments passed through to a constructor, the validates decorator should be places on the class itself:
@validates(typ(string))
class SomeClass(object):
def __init__(self, username):
self.username = username
Additional Clauses:
There are some more complex clauses included with the package:
-
_
: The underscore only allowsNoneType
. -
numeric
: Only acceptsint
,float
, orlong
types. -
text
: Only accepts instances ofbasestring
(Python 2) orstr
(Python 3). -
positive
: Only positive numbers -
negative
: Only positive numbers -
email_address
: Simple regex email check (covers most basic examples) -
ip_address
: Only accept an IPv4 address -
url
: Simple regex url check (covers most basic examples)
These can be found in the validoot.builtins
module.
FAQ:
What if I don’t want validation for one of the position arguments?
Simple. Just use None
.
from validoot import validates, inst, between
@validates(inst(basestring), None, between(0, 100))
def do_something(name, id, age):
pass
What validation clauses are built in?
-
typ(t)
- value must be of exact typet
-
inst(t)
- value must be of exact typet
or of a subclass -
between(lower, upper, lower_inc=True, upper_inc=False)
- the value must betweenlower
andupper
.lower_inc
andupper_inc
indicate range inclusivity. -
len_between(...)
- identical tobetween
but useslen(value)
-
regex(string)
- value must match the regex string provided -
list_of(v)
- value must be a list of objects that pass the validationv
-
dict_of(v1, v2)
- value must be a dictionary where each key passes validationv1
and each value passes validationv2
How do I create my own validation clauses?
The built in clauses provided by Validoot are all subclasses of the
validoot.clauses.Clause
object. Check out its source code to see
how they work. Technically clauses can be any callable object so plain
functions or lambdas also work.