Shorten text repr for DataTree

* only show max 12 children in text ``DataTree`` repr * use ``set_options(display_max_rows=12)`` to configure this setting * always include last item in ``DataTree`` * insert "..." before last item in ``DataTree``
pydata · dcherian · Apr 28, 2025 · Mar 17, 2025 · Mar 17, 2025 · Mar 18, 2025
commit c34530b3b7cb36b70ff0b6c0995c73bf3c14534b
diff --git a/xarray/core/datatree_render.py b/xarray/core/datatree_render.py
@@ -79,6 +79,7 @@ def __init__(
         style=None,
         childiter: type = list,
         maxlevel: int | None = None,
+        maxchildren: int | None = None,
     ):
         """
         Render tree starting at `node`.
@@ -88,6 +89,10 @@ def __init__(
                 Iterables that change the order of children  cannot be used
                 (e.g., `reversed`).
             maxlevel: Limit rendering to this depth.
+            maxchildren: Limit number of children to roughly this number. In practice,
+                for an arbitrarily large DataTree the number of children returned
+                will be (maxchildren * maxchildren - 1) / 2. The last child is also
+                included.
         :any:`RenderDataTree` is an iterator, returning a tuple with 3 items:
         `pre`
             tree prefix.
@@ -160,6 +165,14 @@ def __init__(
         root
         ├── sub0
         └── sub1
+
+        # `maxchildren` roughly limits the total number of children
+
+        >>> print(RenderDataTree(root, maxchildren=3))
+        root
+        ├── sub0
+        │   ├── sub0B
+        └── sub1
         """
         if style is None:
             style = ContStyle()
@@ -169,20 +182,36 @@ def __init__(
         self.style = style
         self.childiter = childiter
         self.maxlevel = maxlevel
+        self.maxchildren = maxchildren
 
     def __iter__(self) -> Iterator[Row]:
         return self.__next(self.node, tuple())
 
     def __next(
-        self, node: DataTree, continues: tuple[bool, ...], level: int = 0
+        self,
+        node: DataTree,
+        continues: tuple[bool, ...],
+        level: int = 0,
+        nchildren: int = 0,
     ) -> Iterator[Row]:
         yield RenderDataTree.__item(node, continues, self.style)
         children = node.children.values()
         level += 1
         if children and (self.maxlevel is None or level < self.maxlevel):
             children = self.childiter(children)
             for child, is_last in _is_last(children):
-                yield from self.__next(child, continues + (not is_last,), level=level)
+                nchildren += 1
+                if (
+                    self.maxchildren is None
+                    or nchildren < self.maxchildren
+                    or (not any(continues) and is_last)
+                ):
+                    yield from self.__next(
+                        child,
+                        continues + (not is_last,),
+                        level=level,
+                        nchildren=nchildren,
+                    )
 
     @staticmethod
     def __item(

diff --git a/xarray/core/formatting.py b/xarray/core/formatting.py
@@ -1137,14 +1137,24 @@ def _datatree_node_repr(node: DataTree, show_inherited: bool) -> str:
 
 def datatree_repr(dt: DataTree) -> str:
     """A printable representation of the structure of this entire tree."""
-    renderer = RenderDataTree(dt)
+    max_rows = OPTIONS["display_max_rows"]
+
+    renderer = RenderDataTree(dt, maxchildren=max_rows)
 
     name_info = "" if dt.name is None else f" {dt.name!r}"
     header = f"<xarray.DataTree{name_info}>"
 
     lines = [header]
     show_inherited = True
-    for pre, fill, node in renderer:
+
+    rendered_items = list(renderer)
+    for i, (pre, fill, node) in enumerate(rendered_items):
+        if len(rendered_items) > max_rows:
+            if i == max_rows:
+                lines.append("...")
+            if i >= max_rows and i != (len(rendered_items) - 1):
+                continue
+
         node_repr = _datatree_node_repr(node, show_inherited=show_inherited)
         show_inherited = False  # only show inherited coords on the root