pyoload

Hy pythonista! I'm happy to present to you pyoload, as from my words:

A python module for extended and recursive type checking and casting of function arguments and class attributes during runtime

Here we use some of the beautiful and clean features offered by python, including decorators and descriptors to help you type check during runtime

Here are some simple usage examples to fill this pypi page.

annotate

This decorator function uses the power of inspect.signature to check the arguments passed to the function using it's annotations with support for default values, generic aliase and annotations adding some more annotation types for convenience, lower some code.

from pyoload import *

@annotate
def foo(
    a: str,     # this has an annotation
    b=3,        # this uses a default value
    c: int = 0  # here both
) -> tuple[str, int]:  # The return type
    ...

from pyoload import *

@annotate
def foo(
    b=dict[str | int, float],     # here a GenericAlias
    c: Cast(list[int]) = '12345'  # here a recursive cast
):  # No return type
    ...

multimethod

This uses the same principles as annotate but allows multiple dispatching (a.k.a runtime overloading?) of functions.

from pyoload import *

@multimethod
def foo(a, b):
    print("two arguments")

@multimethod
def foo(a: Values((1, 2, 3))):
    print('either 1, 2 or 3')

@foo.overload
def _(a: Any):
    raise ValueError()

annotations

These are what pyoload adds to the standard annotations:

Note

The added annotations are still not mergeable with the standard types.

pyoload.Values

A simple tuple subclass, use them as annotation and it will validate only included values.

@annotate
def foo(bar: Values(range(5))):
    ...

pyoload.Cast

This performs recursive casting of the passed arguments into the specified type It supports dict generic aliases as dict[str, int | str] and tries cast in the specified order when the type is a Union.

@annotate
def foo(bar: Cast(tuple[int | str])):
    print(bar)

foo((3, "3"))  # (3, 3)
foo((3j, " "))  # ('3j', ' ')

pyoload.Checks

Permits You tou use custom checker methods, e.g

from pyoload import *

test = lambda val: True  # put your check here

def foo(a: Checks(func=test):
    ...

If the check name is prepended with a _, it will be negated, and an exception is raised if it fails. You can register your own checks using Check.register, as

@Check.register('mycheck')
def _(param, value):
    print(param, value)

Checks(mycheck='param')('val')  # Will raise error on check failure

@annotate
def foo(a: Checks(mycheck='param')):
    ...

Checks can be used as annotations; called using pyoload.Checks as Checks(foo=bar)(val); or Invoked directly using pyoload.Checks as: Check.check(name, param, arg)

len

Receives as argument an integer value specified the expected length or a slice in which the length should be found

gt, lt, eq

Compares grater than, less than and aqual to from the parameter to the value.

func

Uses a function for validation, the function could return a boolean or raise an error. It could be passed directly as positional arguments to pyoload.Checks as: Checks(func1, func2, foo=bar, foo2=bar2)

Checked and casted attributes

CheckedAttr and CastedAttr, are simple descriptors which will perform the casting or checks on assignment.

from pyoload import *

class address:
    number = CastedAttr(tuple[int])
    

The values are checked or casted on assignment

Note

The attributes will return None if not yet initialized