python 之文件操作

一.文件基本操作

　　1.文件的打开　

打开文件时，需要指定文件路径和以何等方式打开文件，打开后，即可获取该文件句柄，日后通过此文件句柄对该文件操作　　

　　　文件句柄 = open('文件路径', '模式')

2.文件的读取

>>> f = open("f:/test.txt", "r")
>>> f.read()
'hello,world'
>>> f.close

　　3.打开文件的模式有：　　

• r ，只读模式【默认】
• w，只写模式【不可读；不存在则创建；存在则清空内容；】
• x， 只写模式【不可读；不存在则创建，存在则报错】
• a， 追加模式【可读；   不存在则创建；存在则只追加内容；】

"+" 表示可以同时读写某个文件

• r+， 读写【可读，可写】
• w+，写读【可读，可写】
• x+ ，写读【可读，可写】
• a+， 写读【可读，可写】

>>> f = open("f:/test.txt", 'r+')
>>> f.read()
'heheo,world~~'
>>> f.write("\naaaaaaa")
8
>>> f.tell()
22
>>> f.read()
''
>>> f.tell()
22
>>> f.seek(0)
0
>>> f.read()
'heheo,world~~\naaaaaaa'

"b"表示以字节的方式操作

• rb  或 r+b
• wb 或 w+b
• xb 或 w+b
• ab 或 a+b

#以二进制文件写
f = open("file.txt", "wb")
str_data = "呵呵"
bytes_data = bytes(str_data, encoding='utf-8')
f.write(bytes_data)
f.close()

#以二进制文件读
f = open("file.txt",'rb')
data = f.read()
f.close()
print(data)
str_data = str(data,encoding="utf-8")
print(str_data)

注：以b方式打开时，读取到的内容是字节类型，写入时也需要提供字节类型

　　4. r+, w+, x+, a+ 区别

　　r+ 可读，可写，若文件不存在会报错，根据指针位置可写随意位置

　　w+ 可写，可读，若文件不存在会创建，在进行写操作会清空文件内容

　　x+ 可写，可读，若文件存在会报错，不存在则创建

　　a+ 可写，可读，只能追加在文件尾部

5.文件内部支持操作：

readline()   逐行读取数据

#逐行去读，较省内存
f = open('log','r')
result = list()
for line in open('log'):
    line = f.readline()
    print(line)
    result.append(line)
print(result)
f.close() 

trancate()，从文件的首行首字符开始截断，截断文件为n个字符；无n表示从当前位置起截断；截断之后n后面的所有字符被删除

>>> with open("f:/test.txt" , 'r+') as f:
...     f.seek(2)
...     f.truncate(3)
...
2
3
>>> with open("f:/test.txt" , 'r+') as f:
...     f.read()
...
'hel'

read(),读取文件内容

>>> with open("f:/test.txt" , 'r+') as f:
...     f.read()
...
'hel'

write(),写入内容

>>> with open("f:/test.txt" , 'r+') as f:
...     f.read()
...     f.write('llo' + '\n' + 'test')
...     f.seek(0)
...     f.read()
...
'hel'
8
0
'helllo\ntest'

readlines(), 将文件内容以列表的形式存放,---->[“第一行”, "第二行"]　

>>> with open("f:/test.txt" , 'r+') as f:
...     temp = f.readlines()
...     print(temp)
...
['heheo,world~~\n', 'aaaaaaa']

open(),打开文件

>>> f = open('f:/test.txt', 'r')

close(),关闭文件

 f.close()

flush(),强行刷入硬盘　　

tell()  获取指针位置
seek()  跳转到某个位置

二.管理上下文

为了避免打开文件后忘记关闭，可以通过管理上下文

with open("log", 'r+') as f:
    data = f.read()
    print(data)

三.练习 

编写脚本实现 ，用户登录，注册，改密，删除功能

#!/usr/bin/env python
# -*- coding:utf-8 -*-
#删除用户，修改密码
def login(username, password):
    """
    用户登录验证
    :param username: 用户名
    :param password: 密码
    :return: True成功，False失败
    """
    f = open('log', 'r', encoding='utf-8')
    for line in f:
        line = line.strip()
        userlist = line.split('$')
        if username == userlist[0] and password == userlist[1]:
            return True
    return False

def user_ex(username):
    """
    用于检测用户是否存在
    :param username: 用户名
    :return: True 表示存在，False用户不存在
    """
    with open('log','r',encoding='utf-8') as f:
        for line in f:
            line = line.strip()
            userlist = line.split('$')
            if username in userlist:
                return True
    return False

def res(username, password):
    """
    用于用户注册
    :param username: 用户名
    :param password: 密码
    :return: True注册成功
    """
    with open('log','a',encoding='utf-8') as f:
        temp = "\n" + username + "$" + password
        f.write(temp)
    return True

def change_pwd(username, password):
    """
    用户修改密码
    :param username: 用户名
    :param password: 修改后的密码
    :return: True修改成功，False修改失败
    """
    file_object = open('log')
    try:
        lines=open('log','r').readlines()
        for i in range(len(lines)):
            if username in lines[i]:
                test=lines[i].split('$')[1]
                lines[i]=lines[i].replace(test,password)
                open('log','w').writelines(lines)
                return True
        return False
    finally:
        file_object.close( )

def del_user(username):
    """
    删除用户
    :param username: 要删除用户名
    :return: true 删除成功，False用户名不在列表中
    """
    file_object = open('log')
    try:
        lines = open('log', 'r').readlines()
        for i in range(len(lines)):
            if username in lines[i]:
                del lines[i]
                print(lines)
                open('log','w').writelines(lines)
                return True
            else:
                return False
    finally:
        file_object.close()

# def del_user(username):
#     with open('log', 'r') as f:
#         for line in f:
#             if re.match("lisi", line):
#                 pass
#             else:
#                 data = line
#     with open('log', 'w+') as f:
#         f.write(data)
#         return True
#     return False

def main():
    inp = input("1:登录；2:注册；3：删除用户；4：修改密码")
    user = input("请输入用户名：")
    pwd = input("请输入密码：")
    if inp == "":
        ret = login(user, pwd)
        if ret:
            print("登录成功")
        else:
            print("登录失败")
    elif inp == "":
        is_ex = user_ex(user)
        if is_ex:
            print("用户已存在,无法注册")
        else:
            resgister = res(user, pwd)
            if resgister:
                print("用户已成功注册")
            else:
                print("注册失败")
    elif inp == "":
        del_us = del_user(user)
        if del_us:
            print("已删除")
        else:
            print("无此用户")
    elif inp == "":
        is_chage = change_pwd(user, pwd)
        if is_chage:
            print("修改成功")
        else:
            print("无此用户")

main()

2.haproxy配置文件更改操作

需求:

　　1.匹配值 ，并将匹配到的内容以列表形式返回给用户

　　2.插入内容，用户input数据后，将数据更新至配置文件中

global
        log 127.0.0.1 local2
        daemon
        maxconn 256
        log 127.0.0.1 local2 info
defaults
        log global
        mode http
        timeout connect 5000ms
        timeout client 50000ms
        timeout server 50000ms
        option  dontlognull

listen stats :8888
        stats enable
        stats uri       /admin
        stats auth      admin:1234

frontend oldboy.org
        bind 0.0.0.0:80
        option httplog
        option httpclose
        option  forwardfor
        log global
        acl www hdr_reg(host) -i www.oldboy.org
        use_backend www.oldboy.org if www

backend www.oldboy.org
        server 100.1.7.9 100.1.7.9 weight 20 maxconn 3000

backend buy.oldboy.org
        server 100.1.7.90 100.1.7.90 weight 20 maxconn 3000

配置文件

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

def fetch(backend):
    result = []
    with open('ha.conf', 'r') as f:
        flag = False
        for line in f:
            if line.strip().startswith('backend') and line.strip() == "backend " + backend:
                flag = True
                continue
            if flag and line.strip().startswith('backend'):
                break
            if flag and line.strip():
                result.append(line.strip())

    return result

def add(backend, record):
    result = fetch(backend)
    if not result:
        # 无backend，无record
        pass
    else:
        # 有backend
        if record in result:
            # 记录record
            pass
        else:
            result.append(record)
            with open('ha.conf', 'r') as old, open('new.conf', 'w') as new:
                continue_flag = False
                for line in old:

                    if line.strip().startswith('backend') and line.strip() == "backend " + backend:
                        continue_flag = True
                        new.write(line)
                        for temp in result:
                            new.write(" "*8 + temp + "\n")
                        continue

                    if continue_flag and line.strip().startswith('backend'):
                        continue_flag = False

                    if continue_flag:
                        pass
                    else:
                        new.write(line)

def add2(backend, record):
    with open('ha.conf', 'r') as old, open('new.conf', 'w') as new:
        in_backend = False
        has_backend = False
        has_record = False
        for line in old:
            if line.strip().startswith('backend') and line.strip() == "backend " + backend:
                has_backend = True
                in_backend = True
                new.write(line)
                continue

            if in_backend and line.strip().startswith('backend'):
                if not has_record:
                    new.write(" "*8 + record + '\n')
                new.write(line)
                in_backend = False
                continue

            if in_backend and line.strip() == record:
                has_record = True
                new.write(line)
                continue

            if line.strip():
                new.write(line)

        if not has_backend:
            # 写backend，写record
            new.write('backend '+ backend + '\n')
            new.write(' '*8 + record + '\n')

# ret = fetch("www.oldboy.org")
# print(ret)

# add('www.oldboy.org', "server 100.1.7.10 100.1.7.10 weight 20 maxconn 3000")
# add2('www.oldboy.org', "server 100.1.7.11 100.1.7.11 weight 20 maxconn 3000")

3. 号码段截取

需求：

　　将文件中的第二列前三字节和后四字节以逗号分开，文件格式如下：

1,"1300000","山东","济南","中国联通","0531","250000"
2,"1300001","江苏","常州","中国联通","0519","213000"
3,"1300002","安徽","巢湖","中国联通","0565","238000"
4,"1300003","四川","宜宾","中国联通","0831","644000"
5,"1300004","四川","自贡","中国联通","0813","643000"

　　需求目标：

1,"130","0000","山东","济南","中国联通","0531","250000"

代码实现：

def phone():
    with open("mobile", "w+") as nf, open("Mobile.txt", "r") as f:
        for row in f:
            row = row.strip().split(',')
            row = (row[:1] + [row[1][:4]+'"', '"' + row[1][4:]] + row[2:])
            nf.write(str(row).strip('[]').replace('" ', "")+'\n')