Search code examples
python-3.xminheapq

Is there a function in Python3 to copy the 3 smallest values in a row into a data frame, for m rows?

I'm trying to find the three smallest values for each row of a dataframe, and put them in a separate dataframe. I don't need to know which column they came from, but I do need to cycle through m rows where m might change for each dataframe I use.

I wanted to use heaps.nsmallest, but I'm not sure how to loop through each row and add the results to a new line of a dataframe each time. I seem to just get a single line of results as output.

 for x in range(len(df1)):
        heap=pd.DataFrame(heapq.nsmallest(3, df1[x]))

I expected this to loop through values of x, but it only produces one column with len(df1) rows. I think it's overwriting the previous results, as it always gives the three minimum values from the last row.

Solution 
  • df2 = pd.DataFrame([heapq.nsmallest(3, df1[x])
                   for x in range(len(df1))])

    or, use sorted(df1[x])[:3]