1、读写文件

#!/usr/bin/env python
# -*- coding:utf-8 -*-
# @Time    : 2018/1/25 20:49
# @Author  : zhouyuyao
# @File    : demonWrite.py
# PyCharm 2017.3.2 (Community Edition)
# Build #PC-173.4127.16, built on December 19, 2017
# JRE: 1.8.0_152-release-1024-b8 amd64
# JVM: OpenJDK 64-Bit Server VM by JetBrains s.r.o
# Windows 10 10.0
# Python 3.6.1 (v3.6.1:69c0db5, Mar 21 2017, 18:41:36) 
# [MSC v.1900 64 bit (AMD64)] on win32

if __name__== "__main__":
    filename = input("Please input the name of file:")
    f = open(filename,"w")     # 以写的形式打开一个文件
    while 1:         # 1 的效率是最高的
        context = input("Please input context('EOF' will close file): ")
        if context == "EOF":
            f.close()
            break
        else:
            f.write(context)
            f.write("\n")

    fRead = open(filename)
    readContext = fRead.read()
    print("------------start-------------")
    print(readContext)
    print("-------------end--------------")
    fRead.close()

运行结果：

Please input the name of file:z.log
Please input context('EOF' will close file): hello
Please input context('EOF' will close file): the weather is cool
Please input context('EOF' will close file): you have wear more clothes
Please input context('EOF' will close file): EOF
------------start-------------
hello
the weather is cool
you have wear more clothes

-------------end--------------

2、读取文件方法

import codecs

ENCODING = "utf-8"       # 字符集
f = open("z.log",encoding=ENCODING)
print(f.name)            # 文件名
print(f.readline())      # 读取成列表的形式
print(f.readlines())     # 读取成列表的形式

with codecs.open("z.log","r",encoding=ENCODING) as f:
    print(f.read())

3、编码问题

编码：
支持中文的编码：utf-8，gbk，gb2312

decode 解码
encode 编码

在Python2中不定义代码的编码排头，在内容中出现中文时会报错。
Python默认将代码文件内容当做ASCII编码处理，但是ASCII编码不存在中文，因为则会抛出异常。
解决问题之道就是要让Python之道文件中使用的是什么编码形式，对于中文，可以用的常见编码有utf-8，gbk和gb2312等，只需在代码文件的最前端添加如下内容即可：

# -*- coding:utf-8 -*-

Python转码的过程：
原有编码 ——> Unicode编码 ——> 目的编码

python会自动将带中文的字符串解码成Unicode，然后再编码成gbk，因为解码是字典进行的，如果没有指明解码方式，就会使用sys,defaultencoding指明的方式来解码。
方法一：
s.decode("utf-8").encoding("gbk")

4、对文件进行排序

#!/usr/bin/env python
# -*- coding:utf-8 -*-
# @Time    : 2018/1/25 23:06
# @Author  : zhouyuyao
# @File    : sortUIDPasswd.py
# PyCharm 2017.3.2 (Community Edition)
# Build #PC-173.4127.16, built on December 19, 2017
# JRE: 1.8.0_152-release-1024-b8 amd64
# JVM: OpenJDK 64-Bit Server VM by JetBrains s.r.o
# Windows 10 10.0
# Python 3.6.1 (v3.6.1:69c0db5, Mar 21 2017, 18:41:36) 
# [MSC v.1900 64 bit (AMD64)] on win32
import codecs

file = "passwd"
sortfile = "sortpasswd.txt"
filecontext = []
sortuid = []

with codecs.open(sortfile,"wb") as fsort:
    with codecs.open(file,encoding="utf-8") as f:
        filecontext += f.readlines()
        for line in filecontext:
            sortuid.append(int(line.split(":")[2]))
        sortuid.sort()
        for uid in sortuid:
            for line in filecontext:
                if str(uid) == line.split(":")[2]:
                    print(line)
                    fsort.write(line.encode("utf-8"))