numpy - Returns the value of the array when the condition was true on the n -th most recent occurrence -

i have defined function

result = valuewhen(condition, array) 

which returns value of array when condition true on recent occurrence:

import pandas pd pd1 = pd.series([0,0,1,1,0,0,1,0,1,0,0,0,1]) pd2 = pd.series([1,2,3,4,5,6,7,8,9,10,11,12,13])  def valuewhen(a1, a2):     res = pd.series(index=a1.index)      res.loc[a1 == 1] = a2     res = res.ffill().fillna(0)     return res  result = valuewhen(pd1, pd2) 

example:

result = valuewhen(array1, array2)  array1  array2  result      0       1       0      0       2       0      1       3       3      1       4       4      0       5       4      0       6       4      1       7       7      0       8       7      1       9       9      0      10       9      0      11       9      0      12       9      1      13      13 

now want return value of array when condition true on nth recent occurrence:

result = valuewhen(condition, array[, n]) #[if missing n=1] 

example:

result = valuewhen(array1, array2, 1) result2 = valuewhen(array1, array2, 2)  array1  array2  result  result2      0       1       0        0      0       2       0        0      1       3       3        0      1       4       4        3      0       5       4        3      0       6       4        3      1       7       7        4      0       8       7        4      1       9       9        7      0      10       9        7      0      11       9        7      0      12       9        7      1      13      13        9 

what pythonic way add parameter n function?