Creating a DataTree should not modify parent and children in-place #9196
Description
What is your issue?
This violates the well-established Python convention that functions either have a return value or modify arguments in-place. They never do both.
Examples:
- Modifying a parent:
from xarray.core.datatree import DataTree
root = DataTree()
child = DataTree(name='child', parent=root)
print(root)
# <xarray.DataTree>
# Group: /
# └── Group: /child- Modifying children:
from xarray.core.datatree import DataTree
child = DataTree()
root = DataTree(children={'child': child})
print(child)
# <xarray.DataTree 'child'>
# Group: /childThis particularly surprising if a DataTree argument is reused, e.g.,
from xarray.core.datatree import DataTree
child = DataTree()
root = DataTree(children={'child': child})
root2 = DataTree(children={'child2': child})
print(child) # attached to root2
# <xarray.DataTree 'child2'>
# Group: /child2
print(root) # now empty!
# <xarray.DataTree>
# Group: /Here's my suggestion:
- We should make the
DataTreeconstructor make shallow copies of itsDataTreearguments. - We should consider getting rid of the
parentconstructor argument. It is redundant withchildren, and unlike children, parent nodes don't show up in theDataTreerepr, so it's more surprising to see them copied.
CC @TomNicholas