diff --git a/pandas/core/shared_docs.py b/pandas/core/shared_docs.py index 787a03471cf6e..06621f7127da3 100644 --- a/pandas/core/shared_docs.py +++ b/pandas/core/shared_docs.py @@ -178,6 +178,12 @@ `__ for more detailed usage and examples, including splitting an object into groups, iterating through groups, selecting a group, aggregation, and more. + +The implementation of groupby is hash-based, meaning in particular that +objects that compare as equal will be considered to be in the same group. +An exception to this is that pandas has special handling of NA values: +any NA values will be collapsed to a single group, regardless of how +they compare. See the user guide linked above for more details. """ _shared_docs["melt"] = """