python中read，readline，和readlines的区别 并逐行输出

Posted 2021-02-14

python中有神奇的三种读操作：read、readline和readlines

read() ?： 一次性读取整个文件内容。推荐使用read(size)方法，size越大运行时间越长

readline() ?：每次读取一行内容。内存不够时使用，一般不太用

readlines() ? ：一次性读取整个文件内容，并按行返回到list，方便我们遍历

下面看代码：

#!/usr/bin/python
# -*- coding: utf-8 -*-
import linecache

f = open("a.txt")
lines = f.read()
print lines
#for i in lines:
#    print i
#    print "==="
print (type(lines))
f.close()
print 35*"="

fr = open("a.txt")
r = fr.readline()
print(type(r))
#print r
while r:
    print r,
    r = fr.readline()
    print "rrr=",r

fr.close()

print 35*"="

frs = open("a.txt")
rls = frs.readlines()
print(type(rls))
print rls
for i in rls:
    print i,
frs.close()

# 直接输出第二行
test2 = linecache.getline("a.txt", 2)
print ""
print 35*"="
print test2

运行结果如下：

weiruoyu
wangxitong
weironghan
weixi
tiantiankaixin
<type ‘str‘>
===================================
<type ‘str‘>
weiruoyu
rrr= wangxitong

wangxitong
rrr= weironghan

weironghan
rrr= weixi

weixi
rrr= tiantiankaixin
tiantiankaixin rrr= 
===================================
<type ‘list‘>
[‘weiruoyu
‘, ‘wangxitong
‘, ‘weironghan
‘, ‘weixi
‘, ‘tiantiankaixin‘]
weiruoyu
wangxitong
weironghan
weixi
tiantiankaixin 
===================================
wangxitong

参考了其他的文章：
https://www.cnblogs.com/yun1108/p/8967334.html
https://blog.csdn.net/weixin_41656968/article/details/80205717