lsst.afw.typehandling._GenericMap.AutoKeyMeta Class Reference

Inheritance diagram for lsst.afw.typehandling._GenericMap.AutoKeyMeta:

Public Member Functions
	__call__ (cls, *args, **kwargs)

Public Attributes
	TEMPLATE_PARAMS

Protected Member Functions
	_guessKeyType (cls, inputData)

Detailed Description

A metaclass for abstract mappings whose key type is implied by their
constructor arguments.

This metaclass requires that the mapping have a `dict`-like constructor,
i.e., it takes a mapping or an iterable of key-value pairs as its first
positional parameter.

This class differs from `~lsst.utils.TemplateMeta` only in that the dtype
(or equivalent) constructor keyword is optional. If it is omitted, the
class will attempt to infer it from the first argument.

Definition at line 122 of file _GenericMap.py.

Member Function Documentation

__call__()

lsst.afw.typehandling._GenericMap.AutoKeyMeta.__call__	(		cls,
		*	args,
		**	kwargs )

Definition at line 135 of file _GenericMap.py.

    def __call__(cls, *args, **kwargs):  # noqa N805, non-self first param
        if len(cls.TEMPLATE_PARAMS) != 1:
            raise ValueError("AutoKeyMeta requires exactly one template parameter")
        dtypeKey = cls.TEMPLATE_PARAMS[0]
        dtype = kwargs.get(dtypeKey, None)
 
        # Try to infer dtype if not provided
        if dtype is None and len(args) >= 1:
            dtype = cls._guessKeyType(args[0])
            if dtype is not None:
                kwargs[dtypeKey] = dtype
 
        return super().__call__(*args, **kwargs)
 

_guessKeyType()

lsst.afw.typehandling._GenericMap.AutoKeyMeta._guessKeyType ( cls, inputData )

protected

Try to infer the key type of a map from its input.

Parameters
----------
inputData : `~collections.abc.Mapping` or iterable of pairs
    Any object that can be passed to a `dict`-like constructor. Keys
    are assumed homogeneous (if not, a
    `~lsst.afw.typehandling.GenericMap` constructor will raise
    `TypeError` no matter what key type, if any, is provided).

Returns
-------
keyType : `type`
    The type of the keys in ``inputData``, or `None` if the type could
    not be inferred.

Definition at line 149 of file _GenericMap.py.

    def _guessKeyType(cls, inputData):  # noqa N805, non-self first param
        """Try to infer the key type of a map from its input.
 
        Parameters
        ----------
        inputData : `~collections.abc.Mapping` or iterable of pairs
            Any object that can be passed to a `dict`-like constructor. Keys
            are assumed homogeneous (if not, a
            `~lsst.afw.typehandling.GenericMap` constructor will raise
            `TypeError` no matter what key type, if any, is provided).
 
        Returns
        -------
        keyType : `type`
            The type of the keys in ``inputData``, or `None` if the type could
            not be inferred.
        """
        if inputData:
            firstKey = None
            if isinstance(inputData, Mapping):
                # mapping to copy
                firstKey = iter(inputData.keys()).__next__()
            elif not isinstance(inputData, str):
                # iterable of key-value pairs
                try:
                    firstKey = iter(inputData).__next__()[0]
                except TypeError:
                    # Not an iterable of pairs
                    pass
            if firstKey:
                return type(firstKey)
        # Any other input is either empty or an invalid input to dict-like constructors
        return None

Member Data Documentation

TEMPLATE_PARAMS

lsst.afw.typehandling._GenericMap.AutoKeyMeta.TEMPLATE_PARAMS

Definition at line 136 of file _GenericMap.py.

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The documentation for this class was generated from the following file:

• /j/snowflake/release/lsstsw/stack/lsst-scipipe-8.0.0/Linux64/afw/g5a732f18d5+53520f316c/python/lsst/afw/typehandling/_GenericMap.py