metaparams 1.0.0

MetaClass supporting fine grained control of object creationand initialization

metaparams

metaparams is a MetaClass/Class/Decorator infrastructure to define params without invoking objects and have them automatically parse/remove the kwargs passed to the class in which they are intalled

Documentation

Read the full documentation at readthedocs.org:

• metaparams documentation

Python 2/3 Support

• Python 2.7

• Python 3.2/3.3/3.4/3.5

• It also works with pypy and pypy3

Installation

From pypi:

pip install metaparams

From source:

• Place the metaparams directory found in the sources inside your project

Features:

• metaparams decorator to params-enable any class

• ParamsBase a class from which to subclass to also be params-enabled

• MetaParams a MetaClass for more complex usage pattern

Quick Usage

With the decorator:

from metaparams import metaparams


@metaparams()
class A(object):

    params = (
        ('p1', True, 'doc'),
        ('p2', 99),
    )

    def __init__(self):
        pass

a = A()

# Defined params are reachable below the attribute params
print(a.params.p1)
print(a.params.p2)

# Modification of default values can be checked
assert a.params._isdefault('p1')

# Inheriting with modification an extension
class B(A):

    params = (
        ('p1', False,),  # changed default value of p1
        ('p3', None),  # new parameter
    )

    def __init__(self):
        pass

b = B()

# Defined params are reachable below the attribute params
print(b.params.p1)
print(b.params.p2)
print(b.params.p3)

# Modification of default values can be checked
assert b.params._isdefault('p1')

# Over the class we can also check defaults
# B has different default value for p1 than A
assert b.params.p1 != A.params._default('p1')

# The name of the attribute 'params' can be changed
# and a shorter alias (PEP-8 ...) added
@metaparams(_pname='kargs', _pshort=True)
class A(object):

    kargs = (
        ('p1', True, 'doc'),
        ('p2', 99),
    )

    def __init__(self):
        pass

a = A()

# Defined params are reachable below the attribute params
print(a.kargs.p1)
print(a.kargs.p2)

print(a.k.p1)
print(a.k.p2)

# Modification of default values can be checked
assert a.kargs._isdefault('p1')


# The metaclass works also so ... but it's a metaclass

class A(MetaParams.as_metaclass(_pname='kargs', _pshort=True)):

    kargs = (
        ('p1', True, 'doc'),
        ('p2', 99),
    )

    def __init__(self):
        pass

a = A()

# Defined params are reachable below the attribute params
print(a.kargs.p1)
print(a.kargs.p2)

print(a.k.p1)
print(a.k.p2)

# Modification of default values can be checked
assert a.kargs._isdefault('p1')


# And finally an already cooked base class with no customization
class A(ParamsBase):

    params = (
        ('p1', True, 'doc'),
        ('p2', 99),
    )

    def __init__(self):
        pass

a = A()

# Defined params are reachable below the attribute params
print(a.params.p1)
print(a.params.p2)

# Modification of default values can be checked
assert a.params._isdefault('p1')