写入csv：
with open(birth_weight_file,'w') as f:
writer=csv.writer(f)
writer.writerow(birth_header)
writer.writerows(birth_data)
f.close()
这种写法最终的结果就是生成的csv文件每两行中间都有一行空白行，解决办法就是写入后面加上newline=''
写法：
with open(birth_weight_file,'w',newline='') as f:
writer=csv.writer(f)
writer.writerow(birth_header)
writer.writerows(birth_data)
f.close()