'Product'    'AmountPaid'
 none            0
 q1              1
 q123            123
 q12_a123        12

for i in range(0,1000000):
   if 'q' not in df.loc[i,'Product']:
      df.loc[i,'AmountPaid']=0
   else:
      # set 'AmountPaid' to the number following 'q'