Struct

class lsst.pipe.base.Struct(**keyArgs)

Bases: object

A container to which you can add fields as attributes.

Parameters:

keyArgs

keyword arguments specifying fields and their values.

Notes

Intended to be used for the return value from run and other Task methods, and useful for any method that returns multiple values.

The intent is to allow accessing returned items by name, instead of unpacking a tuple. This makes the code much more robust and easier to read. It allows one to change what values are returned without inducing mysterious failures: adding items is completely safe, and removing or renaming items causes errors that are caught quickly and reported in a way that is easy to understand.

The primary reason for using Struct instead of dict is that the fields may be accessed as attributes, e.g. aStruct.foo instead of aDict["foo"]. Admittedly this only saves a few characters, but it makes the code significantly more readable.

Struct is preferred over named tuples, because named tuples can be used as ordinary tuples, thus losing all the safety advantages of Struct. In addition, named tuples are clumsy to define and Structs are much more mutable (e.g. one can trivially combine Structs and add additional fields).

Examples

>>> myStruct = Struct(
>>>     strVal = 'the value of the field named "strVal"',
>>>     intVal = 35,
>>> )

Methods Summary

copy()	Make a one-level-deep copy (values are not copied).
getDict()	Get a dictionary of fields in this struct.
mergeItems(struct, *nameList)	Copy specified fields from another struct, provided they don’t already exist.

Methods Documentation

copy()

Make a one-level-deep copy (values are not copied).

Returns:

copy : Struct

One-level-deep copy of this Struct.

getDict()

Get a dictionary of fields in this struct.

Returns:

structDict : dict

Dictionary with field names as keys and field values as values. The values are shallow copies.

mergeItems(struct, *nameList)

Copy specified fields from another struct, provided they don’t already exist.

Parameters:

struct : Struct

Struct from which to copy.

*nameList : str

All remaining arguments are names of items to copy.

Raises:

RuntimeError

Raised if any item in nameList already exists in self (but any items before the conflicting item in nameList will have been copied).

Examples

For example:

foo.copyItems(other, "itemName1", "itemName2")

copies other.itemName1 and other.itemName2 into self.