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 `~lsst.pipe.base.Task.run` and other `~lsst.pipe.base.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,
>>> )
Definition at line 26 of file struct.py.
def lsst.pipe.base.struct.Struct.mergeItems |
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self, |
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struct, |
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* |
nameList |
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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.
Definition at line 96 of file struct.py.
96 def mergeItems(self, struct, *nameList):
97 """Copy specified fields from another struct, provided they don't already exist.
102 `Struct` from which to copy.
104 All remaining arguments are names of items to copy.
109 Raised if any item in nameList already exists in self (but any items before the conflicting item
110 in nameList will have been copied).
116 foo.copyItems(other, "itemName1", "itemName2")
118 copies ``other.itemName1`` and ``other.itemName2`` into self.
120 for name
in nameList:
121 self.__safeAdd(name, getattr(struct, name))