lsst.afw.table._source.SourceCatalog Class Reference

Public Member Functions
def	getChildren (self, parent, *args)

Detailed Description

Definition at line 32 of file _source.py.

Member Function Documentation

getChildren()

def lsst.afw.table._source.SourceCatalog.getChildren	(		self,
			parent,
		*	args
	)

Return the subset of self for which the parent field equals the
given value.

In order for this method to return the correct result, it must be
sorted by parent (i.e. self.isSorted(SourceTable.getParentKey()) must
be True).  This is naturally the case with SourceCatalogs produced by
the detection and deblending tasks, but it may not be true when
concatenating multiple such catalogs.

Additional Catalogs or sequences whose elements correspond in order to
the records of self (i.e. ``zip(self, *args)`` is valid) will be
subset using the same slice object used on self, and these subsets
will be returned along with the subset of self.

Parameters
----------
parent : `int` or `iterable` of `int`
    ID(s) of the parent(s) to get children for.
args : `~lsst.afw.table.Catalog`
    Additional catalogs to subset for the children to return.

Returns
-------
children : a single iterable of `~lsst.afw.table.SourceRecord`
    Children sources if ``parent`` is of type `int`, or a generator
    yielding a `~lsst.afw.table.SourceRecord`s Children sources for
    each parent if ``parent`` is an `iterable`.

Raises
------
AssertionError
    Raised if the catalog is not sorted by the parent key.

Notes
-----
Each call to this function checks if the catalog is sorted, which is
of O(n) complexity, while fetching the children is of O(log n). To
minimize the computational overhead, it is preferable to prepare an
iterable of parent ids for which the children need to be fetched and
pass the iterable as ``parent``.

Definition at line 34 of file _source.py.

    def getChildren(self, parent, *args):
        """Return the subset of self for which the parent field equals the
        given value.
 
        In order for this method to return the correct result, it must be
        sorted by parent (i.e. self.isSorted(SourceTable.getParentKey()) must
        be True).  This is naturally the case with SourceCatalogs produced by
        the detection and deblending tasks, but it may not be true when
        concatenating multiple such catalogs.
 
        Additional Catalogs or sequences whose elements correspond in order to
        the records of self (i.e. ``zip(self, *args)`` is valid) will be
        subset using the same slice object used on self, and these subsets
        will be returned along with the subset of self.
 
        Parameters
        ----------
        parent : `int` or `iterable` of `int`
            ID(s) of the parent(s) to get children for.
        args : `~lsst.afw.table.Catalog`
            Additional catalogs to subset for the children to return.
 
        Returns
        -------
        children : a single iterable of `~lsst.afw.table.SourceRecord`
            Children sources if ``parent`` is of type `int`, or a generator
            yielding a `~lsst.afw.table.SourceRecord`s Children sources for
            each parent if ``parent`` is an `iterable`.
 
        Raises
        ------
        AssertionError
            Raised if the catalog is not sorted by the parent key.
 
        Notes
        -----
        Each call to this function checks if the catalog is sorted, which is
        of O(n) complexity, while fetching the children is of O(log n). To
        minimize the computational overhead, it is preferable to prepare an
        iterable of parent ids for which the children need to be fetched and
        pass the iterable as ``parent``.
        """
        if not self.isSorted(SourceTable.getParentKey()):
            raise AssertionError(
                "The table is not sorted by parent, so cannot getChildren")
 
        def _getChildrenWithoutChecking(parent):
            """Return the subset of self for which the parent field equals the
            given value.
 
            This function works as desired only if `self` is sorted by the
            parent key, but does not check if it is sorted. This function must
            be used only after ensuring outside of the function that
            self.isSorted(SourceTable.getParentKey() evaluates to True.
 
            Parameter
            ---------
            parent : `int`
                ID of the parent to get children for.
 
            Returns
            -------
            children : iterable of `~lsst.afw.table.SourceRecord`
                Children sources.
            """
            s = self.equal_range(parent, SourceTable.getParentKey())
            if args:
                return (self[s],) + tuple(arg[s] for arg in args)
            else:
                return self[s]
 
        try:
            return (_getChildrenWithoutChecking(p) for p in parent)
        except TypeError:
            return _getChildrenWithoutChecking(parent)

---

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

• /j/snowflake/release/lsstsw/stack/lsst-scipipe-0.7.0/Linux64/afw/22.0.1-32-g5ddfab5d3+60ce4897b0/python/lsst/afw/table/_source.py