python文件读写

1. 最基本的读文件方法：

File: readline-example-1.py

file = open("sample.txt")
while 1:
    line = file.readline()
    if not line:
        break
    pass # do something

一行一行得从文件读数据，显然比较慢；不过很省内存。

2. 用fileinput模块

# File: readline-example-2.py

import fileinput

for line in fileinput.input("sample.txt"):
    pass

3. 带缓存的文件读取

# File: readline-example-3.py

file = open("sample.txt")

while 1:
    lines = file.readlines(100000)
    if not lines:
        break
    for line in lines:
        pass # do something

在Python 2.2以后，我们可以直接对一个file对象使用for循环读每行数据：

# File: readline-example-5.py

file = open("sample.txt")

for line in file:
    pass # do something

而在Python 2.1里，你只能用xreadlines迭代器来实现：

# File: readline-example-4.py

file = open("sample.txt")

for line in file.xreadlines():
    pass # do something