The text right above the code says why you can't...
edit:
Let me clarify. From the blog-post:
> since a `DataFrameGroupBy` object doesn’t have a `.query()` or boolean-indexing shortcut of its own, so filtering within groups needs `.apply()` again, and the surrounding pipeline has to be rebuilt around it:
Hence you really do need one of the versions of the code I gave. You can't do the naive approach with just `.groupby().filter(lambda: )`, since you need a row-wise decision.
edit:
Let me clarify. From the blog-post:
> since a `DataFrameGroupBy` object doesn’t have a `.query()` or boolean-indexing shortcut of its own, so filtering within groups needs `.apply()` again, and the surrounding pipeline has to be rebuilt around it:
Hence you really do need one of the versions of the code I gave. You can't do the naive approach with just `.groupby().filter(lambda: )`, since you need a row-wise decision.