Mixing iteration and read methods would lose data

linux环境下，下图1的操作报错，改成图2的形式即可，在windows下不会报错，运行良好，原因有待探究！

ValueError: Mixing iteration and read methods would lose data

lines = fr.readline()

for line in lines[1:]

对于很大的文档，读取的时候逐行读取，提取想要的部分，防止太大内存不够；