flag+文件操作

flag标志位，标识位，在其他语言中可能叫开关，个人觉得当作开关更容易理解。下面我们来利用这个开关来控制文件操作的流程，从而优雅的修改配置文件。

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

原配置文件

我们的需求是：

1、实现fetch获取内容的功能

2、往配置文件中指定位置插入内容的功能

3、删除（或者修改）参数

1、查
    输入：www.oldboy.org
    获取当前backend下的所有记录

2、新建
    输入：
        arg = {
            'bakend': 'www.oldboy.org',
            'record':{
                'server': '100.1.7.9',
                'weight': 20,
                'maxconn': 30
            }
        }

3、删除
    输入：
        arg = {
            'bakend': 'www.oldboy.org',
            'record':{
                'server': '100.1.7.9',
                'weight': 20,
                'maxconn': 30
            }
        }

需求

思路梳理：

1）定义fetch（）函数，函数内容为打开haproxy配置文件，找到backend开头的行，打开开关，找到第二backend开头的行，关闭开关，将开关开启状态下的行添加到我们定义的空列表中。

def fetch(a):
    result=[]
    flag = False
    with open('ha.conf','r')as f:
        for line in f:
            if line.strip()=='backend %s'%a:
                flag=True
                continue
            if flag==True:
                if line.strip().startswith('backend'):
                    flag=False
                else:
                    result.append(line.strip())
    return result
ret=fetch('www.oldboy.org')
print(ret)

2）定义add（）函数：

方法一：把内容添加进列表，然后把列表内容写入。

# a=input('请输入网址：')
# a='www.oldboy.org'
 
# b=input('请输入新纪录字典：')
b='{"backend":"www.oldboy.org","record":{"server":"100.1.7.6","weight":20,"maxconn":30}}'
b=json.loads(b)
a=b["backend"]
s=b["record"]
s="server %s %s weight %s maxconn %s" % (s['server'],s['server'],s['weight'],s['maxconn'])
title='backend %s' % a
l1=chaxun(a)
l1.append(s)
print(l1)
with open('mm') as read_obj, open('nn', 'w') as write_obj:
    flag = False      #默认没有找到目标标题
    has_write = False  #默认列表内容还没有写
    for line in read_obj:
        if line.strip() == title:
            write_obj.write(line)
            flag = True  #找到标题
            continue
        if flag and line.strip().startswith('backend'):
            flag = False  #标题结束
        if flag:   #如果已经找到目标标题
            if not has_write: #如果还没有写内容
                for new_line  in l1:
                    temp = "%s %s 
" %(" "*8, new_line)
                    write_obj.write(temp)
                has_write = True
                #列表内容书写完毕，即使flag=True，即使没遇到下一个backend，也不会书写内容
        else:
    # 写入上下部分
            write_obj.write(line)# a=input('请输入网址：')
# a='www.oldboy.org'
 
# b=input('请输入新纪录字典：')
b='{"backend":"www.oldboy.org","record":{"server":"100.1.7.6","weight":20,"maxconn":30}}'
b=json.loads(b)
a=b["backend"]
s=b["record"]
s="server %s %s weight %s maxconn %s" % (s['server'],s['server'],s['weight'],s['maxconn'])
title='backend %s' % a
l1=chaxun(a)
l1.append(s)
print(l1)
with open('mm') as read_obj, open('nn', 'w') as write_obj:
    flag = False      #默认没有找到目标标题
    has_write = False  #默认列表内容还没有写
    for line in read_obj:
        if line.strip() == title:
            write_obj.write(line)
            flag = True  #找到标题
            continue
        if flag and line.strip().startswith('backend'):
            flag = False  #标题结束
        if flag:   #如果已经找到目标标题
            if not has_write: #如果还没有写内容
                for new_line  in l1:
                    temp = "%s %s 
" %(" "*8, new_line)
                    write_obj.write(temp)
                has_write = True
                #列表内容书写完毕，即使flag=True，即使没遇到下一个backend，也不会书写内容
        else:
    # 写入上下部分
            write_obj.write(line)

方法二：读一行，写一行，直到写到第二个backend，再此之前插入内容即可。

# a=input('请输入网址：')
# a='www.oldboy.org'
 
# b=input('请输入新纪录字典：')
b='{"backend":"www.oldboy.org","record":{"server":"100.1.7.6","weight":20,"maxconn":30}}'
b=json.loads(b)
a=b["backend"]
s=b["record"]
s="server %s %s weight %s maxconn %s" % (s['server'],s['server'],s['weight'],s['maxconn'])
title='backend %s' % a
l1=chaxun(a)
l1.append(s)
print(l1)
with open('mm') as read_obj, open('nn', 'w') as write_obj:
    flag = False      #默认没有找到目标标题
    for line in read_obj:
        if line.strip() == title:
            write_obj.write(line)
            flag = True  #找到标题
            continue
        if flag and line.strip().startswith('backend'):
            write_obj.write("%s%s 
" %(" "*8, s))
            write_obj.write(line)
            flag = False  #标题结束
        else:
    # 写入上下部分
            write_obj.write(line)

整体实现功能，武sir的标准答案：

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


def fetch(backend):
    backend_title = 'backend %s' % backend
    record_list = []
    with open('ha') as obj:
        flag = False
        for line in obj:
            line = line.strip()
            if line == backend_title:
                flag = True
                continue
            if flag and line.startswith('backend'):
                flag = False
                break

            if flag and line:
                record_list.append(line)

    return record_list


def add(dict_info):
    backend = dict_info.get('backend')
    record_list = fetch(backend)
    backend_title = "backend %s" % backend
    current_record = "server %s %s weight %d maxconn %d" % (dict_info['record']['server'], dict_info['record']['server'], dict_info['record']['weight'], dict_info['record']['maxconn'])
    if not record_list:
        record_list.append(backend_title)
        record_list.append(current_record)
        with open('ha') as read_file, open('ha.new', 'w') as write_file:
            flag = False
            for line in read_file:
                write_file.write(line)
            for i in record_list:
                if i.startswith('backend'):
                    write_file.write(i+'
')
                else:
                    write_file.write("%s%s
" % (8*" ", i))
    else:
        record_list.insert(0, backend_title)
        if current_record not in record_list:
            record_list.append(current_record)

        with open('ha') as read_file, open('ha.new', 'w') as write_file:
            flag = False
            has_write = False
            for line in read_file:
                line_strip = line.strip()
                if line_strip == backend_title:
                    flag = True
                    continue
                if flag and line_strip.startswith('backend'):
                    flag = False
                if not flag:
                    write_file.write(line)
                else:
                    if not has_write:
                        for i in record_list:
                            if i.startswith('backend'):
                                write_file.write(i+'
')
                            else:
                                write_file.write("%s%s
" % (8*" ", i))
                    has_write = True
    os.rename('ha','ha.bak')
    os.rename('ha.new','ha')


def remove(dict_info):
    backend = dict_info.get('backend')
    record_list = fetch(backend)
    backend_title = "backend %s" % backend
    current_record = "server %s %s weight %d maxconn %d" % (dict_info['record']['server'], dict_info['record']['server'], dict_info['record']['weight'], dict_info['record']['maxconn'])
    if not record_list:
        return
    else:
        if current_record not in record_list:
            return
        else:
            del record_list[record_list.index(current_record)]
            if len(record_list) > 0:
                record_list.insert(0, backend_title)
        with open('ha') as read_file, open('ha.new', 'w') as write_file:
            flag = False
            has_write = False
            for line in read_file:
                line_strip = line.strip()
                if line_strip == backend_title:
                    flag = True
                    continue
                if flag and line_strip.startswith('backend'):
                    flag = False
                if not flag:
                    write_file.write(line)
                else:
                    if not has_write:
                        for i in record_list:
                            if i.startswith('backend'):
                                write_file.write(i+'
')
                            else:
                                write_file.write("%s%s
" % (8*" ", i))
                    has_write = True
    os.rename('ha','ha.bak')
    os.rename('ha.new','ha')

if __name__ == '__main__':
    """
    print '1、获取；2、添加；3、删除'
    num = raw_input('请输入序号：')
    data = raw_input('请输入内容：')
    if num == '1':
        fetch(data)
    else:
        dict_data = json.loads(data)
        if num == '2':
            add(dict_data)
        elif num == '3':
            remove(dict_data)
        else:
            pass
    """
    #data = "www.oldboy.org"
    #fetch(data)
    #data = '{"backend": "tettst.oldboy.org","record":{"server": "100.1.7.90","weight": 20,"maxconn": 30}}'
    #dict_data = json.loads(data)
    #add(dict_data)
    #remove(dict_data)

demo