Basics

A Python class walks into a bar.

import numpy as np
from numpy.typing import NDArray
from xattree import xattree, has, dim, array

class Foo:
    n: int = dim(default=10)
    a: NDArray[np.float64] = array(default=0., dims=("n",))

def bar(cls):
    return cls if has(cls) else xattree(cls)

FooBar = bar(Foo)

Note: don’t use the function form, just decorate your classes — unless you have good reason, like a joke to make

A short while later it emerges, acting more or less the same, but carrying itself differently — more together, somehow.

fubar = FooBar()
fubar.a

<xarray.DataArray 'a' (n: 10)> Size: 80B
array([0., 0., 0., 0., 0., 0., 0., 0., 0., 0.])
Coordinates:
  * n        (n) int64 80B 0 1 2 3 4 5 6 7 8 9

xarray.DataArray

'a'

• n: 10

• 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0

  array([0., 0., 0., 0., 0., 0., 0., 0., 0., 0.])

• Coordinates: (1)
  • n
    (n)
    int64
    0 1 2 3 4 5 6 7 8 9

    array([0, 1, 2, 3, 4, 5, 6, 7, 8, 9])

You sense deception. Maybe this is not your typical dive, but one of those places young people go for over-priced caffeine.

A few more, these with strange hats and ominous attributes, stride in. You begin to fret.

from xattree import ROOT, field

@xattree
class Grid:
    x: int = dim(default=3, scope=ROOT)
    y: int = dim(default=3, scope=ROOT)

@xattree
class Arrs:
    a: NDArray[np.float64] = array(default=0.0, dims=("x", "y"))

@xattree
class Root:
    grid: Grid = field()
    arrs: Arrs = field()

grid = Grid()
root = Root(grid=grid)
arrs = Arrs(parent=root)

Soon something struts out, doing them a perfect imitation. Be not fooled.

print(root.data)

<xarray.DataTree 'root'>
Group: /
│   Dimensions:  (x: 3, y: 3)
│   Coordinates:
│     * x        (x) int64 24B 0 1 2
│     * y        (y) int64 24B 0 1 2
│   Attributes:
│       host:      Root(grid=Grid(x=3, y=3, name='grid', strict=True), arrs=Arrs(...
│       metadata:  {'grid': {}, 'arrs': {}, 'x': {}, 'y': {}}
├── Group: /grid
│       Attributes:
│           host:      Grid(x=3, y=3, name='grid', strict=True)
│           metadata:  {'x': {}, 'y': {}}
└── Group: /arrs
        Dimensions:  (x: 3, y: 3)
        Data variables:
            a        (x, y) float64 72B 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0
        Attributes:
            host:      Arrs(a=<xarray.DataArray 'a' (x: 3, y: 3)> Size: 72B\narray([[...
            metadata:  {'a': {}}