pandas: complex filter on rows of DataFrame

Question

I would like to filter rows by a function of each row, e.g.

def f(row):
  return sin(row[\'velocity\'])/np.prod([\'masses\']) > 5

df = pandas.DataFrame(.         


        

Answer 1

The best approach I've found is, instead of using reduce=True to avoid errors for empty df (since this arg is deprecated anyway), just check that df size > 0 before applying the filter:

def my_filter(row):
    if row.columnA == something:
        return True

    return False

if len(df.index) > 0:
    df[df.apply(my_filter, axis=1)]