python if statement to check a column for a value and do a command

for z in range(0,countD.shape[0]):
    if countD[z,0] in background_low1[:,0]:
        background_lowCountD.append(countD[z,:])
    else:
        background_goodCountD.append(countD[z,:])  

I'm using the above code and getting a "list indices must be integers, not tuple" error message. I have two uneven arrays (CountD and background_low1), If a value is present in column 0 of both arrays at any row level I want to move that row to a new array, if its only present in 1 I want that row moved to a second new array.