问题
I have a pandas data frame with a column 'id' and a column 'value'. It is already sorted by first id (ascending) and then value (descending). What I need is the top 10 values per id.
I assumed that something like the following would work, but it doesn't:
df.groupby("id", as_index=False).aggregate(lambda (index,rows) : rows.iloc[:10])
What I get is just a list of ids, the value column (and other columns that I omitted for the question) aren't there anymore.
Any ideas how it might be done, without iterating through each of the single rows and appending the first ten to another data structure?
回答1:
Is this what you're looking for?
df.groupby('id').head(10)
来源：https://stackoverflow.com/questions/33168397/pandas-get-top-10-values-after-grouping