参考了https://blog.csdn.net/shandong_chu/article/details/70173952
import sys
方法一：
#read txt method one
f = open("./image/abc.txt")
line = f.readline()
while line:
print line
line = f.readline()
f.close()
方法二：
#read txt method two
f = open("./image/abc.txt")
for line2 in open("./image/abc.txt"):
print line2
方法三：
#read txt method three
f2 = open("./image/abc.txt","r")
lines = f2.readlines()
for line3 in lines:
print line3
