[skip ci] slicing

Author: MarcoGorelli

web/pandas/pdeps/0005-no-default-index-mode.md

@@ -126,6 +126,33 @@ Out[11]: NoRowIndex(len=4)
 
 Appending anything other than another ``NoRowIndex`` would raise.
 
+### Slicing a ``NoRowIndex``
+
+If one has a ``DataFrame`` with ``NoRowIndex``, then one would expect that a slice of it would still have
+a ``NoRowIndex``. This could be accomplished with:
+
+    If a slice of length ``x`` is taken from a ``NoRowIndex`` of length ``y``, then one gets a
+    ``NoRowIndex`` of length ``x``. Label-based slicing would not be allowed.
+
+Example:
+
+```python
+In [12]: df = pd.DataFrame({'a': [1,  2, 3], 'b': [4, 5, 6]}, index=NoRowIndex(3))
+
+In [13]: df.loc[df['a']>1, 'b']
+Out[13]:
+5
+6
+Name: b, dtype: int64
+
+In [14]: df.loc[df['a']>1, 'b'].index
+Out[14]: NoRowIndex(len=2)
+
+In [15]: df.loc[0, 'b']
+---------------------------------------------------------------------------
+IndexError: Cannot use label-based indexing on NoRowIndex!
+```
+
 ### 2. DataFrameFormatter and SeriesFormatter changes
 
 When printing an object with a ``NoIndex``, then the row labels wouldn't be shown: