plato.providers package¶

Contains providers for test data generation.

plato.providers.base module¶

Provider interface and base implemenations of functionality.

The members of this module are of interest if you are implementing your own providers. Otherwise, you probably will not need them.

class plato.providers.base.AttributeProvider(parent, attr_name)[source]¶

Bases: plato.providers.base.Provider[plato.providers.base.T], plato.providers.base.WithAttributeAccess

Provider of an attribute of the samples of another provider.

Parameters

parent – Parent provider to sample.
attr_name – Name of the attribute to provide from the sampled object.

sample(context)[source]¶

Return a single value (sample) for the provider.

Parameters: context (plato.context.Context) – The sampling context. Use the random number generator from the context or initialize your random number generator from the seed provided in the context to ensure reproducibality.
Returns: The sampled value.
Return type: T

class plato.providers.base.Provider(*args, **kwargs)[source]¶

Bases: abc.ABC, Generic[plato.providers.base.T], plato.providers.base.ProviderProtocol[plato.providers.base.T]

Provider interface.

abstract sample(context)[source]¶

Return a single value (sample) for the provider.

Parameters: context (plato.context.Context) – The sampling context. Use the random number generator from the context or initialize your random number generator from the seed provided in the context to ensure reproducibality.
Returns: The sampled value.
Return type: T

class plato.providers.base.ProviderProtocol(*args, **kwargs)[source]¶

Bases: Protocol[plato.providers.base.T]

Defines the Provider protocol.

This should only be used for typing. When implementing a provider use the Provider abstract base class.

sample(context)[source]¶

Return a single value (sample) for the provider.

Parameters: context (plato.context.Context) – The sampling context. Use the random number generator from the context or initialize your random number generator from the seed provided in the context to ensure reproducibality.
Returns: The sampled value.
Return type: T

class plato.providers.base.WithAttributeAccess[source]¶

Bases: Generic[plato.providers.base.T]

Provider mixin to provide transparent access to attributes.

Attributes existing on the implementing class and special members starting and ending with a double-underscore (__) are excluded.

Example

from dataclasses import dataclass

@dataclass
class Dto:
    foo: str = "foo"
    bar: str = "bar"

class DtoProvider(Provider, WithAttributeAccess):
    def sample(self, context: Context) -> Dto:
        return Dto()

print(sample(DtoProvider().foo))

foo

plato.providers.common module¶

Commonly used providers.

class plato.providers.common.Shared(provider)[source]¶

Bases: plato.providers.base.Provider[plato.providers.common.T], plato.providers.base.WithAttributeAccess[plato.providers.common.T]

Share the sampled value of a Provider across multiple fields.

Try to avoid sharing values across more than a single formclass because the semantics of Shared are a bit unintuitive in other cases. But for completeness sake, this is how it works: the first sampled value is reused within the same formclass instance and old child instances. However, if the value is first sampled in a child instance, it will not be reused in the parent instance.

Parameters: provider – Provider to share sampled values of.

Examples

Normal usage:

from dataclasses import asdict
from pprint import pprint

class CountingProvider(Provider):
    def __init__(self):
        self.n = 0

    def sample(self, context: Context) -> int:
        self.n += 1
        return self.n

counting_provider = CountingProvider()

@formclass
class MyFormclass:
    shared: int = Shared(counting_provider)
    same: int = shared
    different: int = counting_provider

pprint(asdict(sample(MyFormclass())))

{'different': 2, 'same': 1, 'shared': 1}

Discouraged use across multiple formclass instances:

counting_provider = CountingProvider()

@formclass
class Child:
    value: int = Shared(counting_provider)

@formclass
class Parent:
    samples_child_first: Child = Child()
    samples_new_value_in_parent: int = samples_child_first.value
    reuses_value_sampled_in_parent: Child = Child()

pprint(asdict(sample(Parent())))

{'reuses_value_sampled_in_parent': {'value': 2},
 'samples_child_first': {'value': 1},
 'samples_new_value_in_parent': 2}

sample(context)[source]¶

Return a single value (sample) for the provider.

Parameters: context (plato.context.Context) – The sampling context. Use the random number generator from the context or initialize your random number generator from the seed provided in the context to ensure reproducibality.
Returns: The sampled value.
Return type: T

plato.providers.faker module¶

Support for using the Faker library with Plato.

class plato.providers.faker.FromFaker(faker=None)[source]¶

Bases: object

Create a Provider from a Faker instance.

All indexing operations and attribute access will be delegated to to the Faker instance, but return Provider instances usable in a formclass.

Parameters: faker – Faker instance used to generate values. If not given a new instance using the default will be created.

Example

fake = FromFaker(Faker(["en-US", "de-DE"]))

print(sample(fake["en-US"].street_address()))
print(sample(fake["de-DE"].street_address()))

413 Perez Cape Apt. 615
Schaafallee 41