Update README.md

Signed-off-by: David Rotermund <54365609+davrot@users.noreply.github.com>

numpy/nested_iters/README.md

@@ -1,4 +1,4 @@
-# zip
+# nested_iters
 {:.no_toc}
 
 <nav markdown="1" class="toc-class">
@@ -23,6 +23,9 @@ numpy.nested_iters(op, axes, flags=None, op_flags=None, op_dtypes=None, order='K
 > 
 > Create a tuple of nditer objects which iterate in nested loops over different axes of the op argument. The first iterator is used in the outermost loop, the last in the innermost loop. Advancing one will change the subsequent iterators to point at its new element.
 
+
+### 2d
+
 ```python
 import numpy as np
 
@@ -53,3 +56,96 @@ iter_a.multi_index: (1,), iter_b.multi_index: (0,)
 iter_a.multi_index: (1,), iter_b.multi_index: (1,)
 iter_a.multi_index: (1,), iter_b.multi_index: (2,)
 ```
+
+### 3d
+
+```python
+import numpy as np
+
+
+a = np.zeros((2, 3, 4))
+print(a.shape) # -> (2, 3, 4)
+
+print("------")
+iter_a, iter_b = np.nested_iters(a, [[0], [1, 2]], flags=["multi_index"])
+
+for x in iter_a:
+    for y in iter_b:
+        print(
+            f"iter_a.multi_index: {iter_a.multi_index}, iter_b.multi_index: {iter_b.multi_index}"
+        )
+print("------")
+
+
+print("++++++")
+iter_a, iter_b = np.nested_iters(a, [[0, 1], [2]], flags=["multi_index"])
+
+for x in iter_a:
+    for y in iter_b:
+        print(
+            f"iter_a.multi_index: {iter_a.multi_index}, iter_b.multi_index: {iter_b.multi_index}"
+        )
+print("++++++")
+```
+
+Output: 
+
+```python
+------
+iter_a.multi_index: (0,), iter_b.multi_index: (0, 0)
+iter_a.multi_index: (0,), iter_b.multi_index: (0, 1)
+iter_a.multi_index: (0,), iter_b.multi_index: (0, 2)
+iter_a.multi_index: (0,), iter_b.multi_index: (0, 3)
+iter_a.multi_index: (0,), iter_b.multi_index: (1, 0)
+iter_a.multi_index: (0,), iter_b.multi_index: (1, 1)
+iter_a.multi_index: (0,), iter_b.multi_index: (1, 2)
+iter_a.multi_index: (0,), iter_b.multi_index: (1, 3)
+iter_a.multi_index: (0,), iter_b.multi_index: (2, 0)
+iter_a.multi_index: (0,), iter_b.multi_index: (2, 1)
+iter_a.multi_index: (0,), iter_b.multi_index: (2, 2)
+iter_a.multi_index: (0,), iter_b.multi_index: (2, 3)
+iter_a.multi_index: (1,), iter_b.multi_index: (0, 0)
+iter_a.multi_index: (1,), iter_b.multi_index: (0, 1)
+iter_a.multi_index: (1,), iter_b.multi_index: (0, 2)
+iter_a.multi_index: (1,), iter_b.multi_index: (0, 3)
+iter_a.multi_index: (1,), iter_b.multi_index: (1, 0)
+iter_a.multi_index: (1,), iter_b.multi_index: (1, 1)
+iter_a.multi_index: (1,), iter_b.multi_index: (1, 2)
+iter_a.multi_index: (1,), iter_b.multi_index: (1, 3)
+iter_a.multi_index: (1,), iter_b.multi_index: (2, 0)
+iter_a.multi_index: (1,), iter_b.multi_index: (2, 1)
+iter_a.multi_index: (1,), iter_b.multi_index: (2, 2)
+iter_a.multi_index: (1,), iter_b.multi_index: (2, 3)
+------
+++++++
+iter_a.multi_index: (0, 0), iter_b.multi_index: (0,)
+iter_a.multi_index: (0, 0), iter_b.multi_index: (1,)
+iter_a.multi_index: (0, 0), iter_b.multi_index: (2,)
+iter_a.multi_index: (0, 0), iter_b.multi_index: (3,)
+iter_a.multi_index: (0, 1), iter_b.multi_index: (0,)
+iter_a.multi_index: (0, 1), iter_b.multi_index: (1,)
+iter_a.multi_index: (0, 1), iter_b.multi_index: (2,)
+iter_a.multi_index: (0, 1), iter_b.multi_index: (3,)
+iter_a.multi_index: (0, 2), iter_b.multi_index: (0,)
+iter_a.multi_index: (0, 2), iter_b.multi_index: (1,)
+iter_a.multi_index: (0, 2), iter_b.multi_index: (2,)
+iter_a.multi_index: (0, 2), iter_b.multi_index: (3,)
+iter_a.multi_index: (1, 0), iter_b.multi_index: (0,)
+iter_a.multi_index: (1, 0), iter_b.multi_index: (1,)
+iter_a.multi_index: (1, 0), iter_b.multi_index: (2,)
+iter_a.multi_index: (1, 0), iter_b.multi_index: (3,)
+iter_a.multi_index: (1, 1), iter_b.multi_index: (0,)
+iter_a.multi_index: (1, 1), iter_b.multi_index: (1,)
+iter_a.multi_index: (1, 1), iter_b.multi_index: (2,)
+iter_a.multi_index: (1, 1), iter_b.multi_index: (3,)
+iter_a.multi_index: (1, 2), iter_b.multi_index: (0,)
+iter_a.multi_index: (1, 2), iter_b.multi_index: (1,)
+iter_a.multi_index: (1, 2), iter_b.multi_index: (2,)
+iter_a.multi_index: (1, 2), iter_b.multi_index: (3,)
+++++++
+```
+
+For higher dimensions, we can partition the indices into groups (if we want to). e.g. 4 dims: ​
+
+[[0,1], [2,3]] or [[0],[1],[2],[3]] or [[0,1,2],[3]],... ​
+