Simple validation for function arguments using a decorator.
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
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 )
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:
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.
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
There are some more complex clauses included with the package:
These can be found in the validoot.builtins module.
Simple. Just use None.
from validoot import validates, inst, between @validates(inst(basestring), None, between(0, 100)) def do_something(name, id, age): pass
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.