lsst.pipe.base.struct.Struct Class Reference

A struct to which you can add any fields. More...

Inheritance diagram for lsst.pipe.base.struct.Struct:

Public Member Functions
def	__init__
	Create a Struct with the specified field names and values. More...
def	getDict
	Return a dictionary of attribute name: value. More...
def	mergeItems
	Copy specified fields from another struct, provided they don't already exist. More...
def	copy
	Return a one-level-deep copy (values are not copied) More...
def	__eq__
def	__len__
def	__repr__

Private Member Functions
def	__safeAdd
	Add a field if it does not already exist and name does not start with __ (two underscores) More...

Private Attributes
	__dict__

Detailed Description

A struct to which you can add any fields.

Intended to be used for the return value from Task.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).

Definition at line 25 of file struct.py.

Constructor & Destructor Documentation

def lsst.pipe.base.struct.Struct.__init__	(		self,
			keyArgs
	)

Create a Struct with the specified field names and values.

For example:

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

Parameters

[in]

**keyArgs

keyword arguments specifying name=value pairs

Definition at line 44 of file struct.py.

    def __init__(self, **keyArgs):
        """!Create a Struct with the specified field names and values

        For example:
        @code
        myStruct = Struct(
            strVal = 'the value of the field named "strVal"',
            intVal = 35,
        )
        @endcode

        @param[in] **keyArgs    keyword arguments specifying name=value pairs
        """
        object.__init__(self)
        for name, val in keyArgs.iteritems():
            self.__safeAdd(name, val)