LazyProperty#

class pyinaturalist.models.LazyProperty(converter, name=None, doc=None, type=<class 'pyinaturalist.models.base.BaseModel'>, **converter_kwargs)#

Bases: property

A lazy-initialized/cached descriptor for attrs classes. Its purpose is similar to @functools.cached_property, but it works for slotted classes by not relying on __dict__.

Currently this is used to lazy-load nested model objects for better performance.

How it’s used:

Define an attrs class
Use add_lazy_attrs as a field_transformer for the class, which adds a temporary attributes
Define a LazyProperty class attribute with a converter

How it works:

During attrs init, the temporary attribute is set containing a raw dict
When foo is first accessed, it runs the converter on the temp attribute
When foo is accessed again, the previously converted temp attribute will be returned

Example:

# Just pretend these are expensive conversion functions
def converter_func(value) -> str:
    return str(value)

def list_converter_func(value) -> List:
    return [value]

@attrs.define(field_transformer=add_lazy_attrs)
class MyModel(BaseModel):
    str_field = LazyProperty(converter_func)
    list_field = LazyProperty(list_converter_func)

    # Auto-generated temp attributes will look like:
    # _str_field = field(default=None)
    # _list_field = field(factory=list)

Attributes

Methods

__init__(converter, name=None, doc=None, type=<class 'pyinaturalist.models.base.BaseModel'>, **converter_kwargs)#

deleter()#: Descriptor to obtain a copy of the property with a different deleter.

get_lazy_attr()#

Get a temp attribute to be used by this LazyProperty instance

Return type: Attribute

getter()#: Descriptor to obtain a copy of the property with a different getter.

setter()#: Descriptor to obtain a copy of the property with a different setter.