读取某个单元格不为空，进行写入，为什么循环会中断

df = xl() var = 1 v = 1 # while var == 1 : for j in range(1,100): df1 = df[0][0] print(df1) if df1 is None: print(123) else: v = v + 1 print(v) write_xl("许1生","L1")