python逐行读取文件，readline,readlines,for,read

参照：https://blog.youkuaiyun.com/enweitech/article/details/78790888

1.readline,优点：节省内存，不需要一次性把文件内容放入内存中缺点：速度相对较慢

f = open("ip.txt", "r", encoding="utf-8")
ret = f.readline()
while ret:
    print(ret, end='')
    ret = f.readline()
f.close()

2.readlines,一次性读取所有行，内存消耗过大

f = open("ip.txt", "r", encoding="utf-8")
for line in f.readlines():
    print(line, end="")

3.直接for循环

for line in open("ip.txt", "r", encoding="utf-8"):
    print(line, end="")

4.read，类似readline

f = open("ip.txt", "r", encoding="utf-8")
ret = f.read(5)
while ret:
    print(ret, end='')
    ret = f.read(5)
f.close()