通过特定的定界符对字符串进行操作并写入文本文件

Ahmed Ayman Ibrahim 发表于 Dev

艾哈迈德·艾曼·易卜拉欣

我正在编写一个函数，该函数将文件updates.txt作为输入。该文件如下所示：

---------------------------------------------------
MRT Header
    Timestamp: 1453939200(2016-01-28 01:00:00)
    Type: 16(BGP4MP)
    Subtype: 4(BGP4MP_MESSAGE_AS4)
    Length: 39
BGP4MP_MESSAGE_AS4
    Peer AS Number: 37989
    Local AS Number: 12654
    Interface Index: 0
    Address Family: 1(IPv4)
    Peer IP Address: 203.123.48.6
    Local IP Address: 193.0.4.28
BGP Message
    Marker: -- ignored --
    Length: 19
    Type: 4(KEEPALIVE)
---------------------------------------------------
MRT Header
    Timestamp: 1453939200(2016-01-28 01:00:00)
    Type: 16(BGP4MP)
    Subtype: 4(BGP4MP_MESSAGE_AS4)
    Length: 118
BGP4MP_MESSAGE_AS4
    Peer AS Number: 1836
    Local AS Number: 12654
    Interface Index: 0
    Address Family: 1(IPv4)
    Peer IP Address: 146.228.1.3
    Local IP Address: 193.0.4.28
BGP Message
    Marker: -- ignored --
    Length: 98
    Type: 2(UPDATE)
    Withdrawn Routes Length: 0
    Total Path Attribute Length: 71
    Path Attribute Flags/Type/Length: 0x40/1/1
        ORIGIN: 0(IGP)
    Path Attribute Flags/Type/Length: 0x40/2/42
        AS_PATH
            Path Segment Type: 2(AS_SEQUENCE)
            Path Segment Length: 10
            Path Segment Value: 1836 174 6453 37282 37088 37629 37629 37629 37629 37629
    Path Attribute Flags/Type/Length: 0x40/3/4
        NEXT_HOP: 146.228.1.3
    Path Attribute Flags/Type/Length: 0xc0/8/12
        COMMUNITY: 1836:110 1836:6000 1836:6031
    NLRI: 154.65.7.0/24
---------------------------------------------------

该文件是一系列“块”。每个块都包含在虚线之间

---------------------------------------------------
# Block (n)
---------------------------------------------------
# Block (n+1)
---------------------------------------------------
# Block (n+2) , etc

我想逐块读取整个文件，并返回仅包含以下字段行的文本文件：时间戳，对等AS编号，本地AS编号，对等IP地址，本地IP地址。

生成的.txt文件应如下所示：

---------------------------------------------------
MRT Header
    Timestamp: 1453939200(2016-01-28 01:00:00)
BGP4MP_MESSAGE_AS4
    Peer AS Number: 37989
    Local AS Number: 12654
    Peer IP Address: 203.123.48.6
    Local IP Address: 193.0.4.28
---------------------------------------------------
MRT Header
    Timestamp: 1453939200(2016-01-28 01:00:00)
BGP4MP_MESSAGE_AS4
    Peer AS Number: 1836
    Local AS Number: 12654
    Peer IP Address: 203.123.48.6
    Local IP Address: 193.0.4.28
---------------------------------------------------

理想情况下，我想用新的文本文件覆盖updates.txt，以免浪费空间，并将其保存在新目录“ Parsed Updates”中。

我知道这是最小的，因为我坚持使用破折号定界符，但是我的代码如下所示：

import sys
import os

def parser(filename):
    info = open(filename, 'r+')
    info.read()

    #Here comes the string manipulation code
    #info.split( '---------------------------------------------------')

    info.close()
    print 'The file has been parsed successfully !!'

def main():
    parser('updates.txt')


if __name__=='__main__':
    main()

山·瓦勒鲁

>>> with open('results.txt', 'wb') as r:
...     with open('updates.txt', 'rb') as u:
...         for line in u.readlines():
...             if '-'*51 in line:
...                 r.write(line)
...             else:
...                 if any(field in line for field in ['Timestamp', 'Peer AS Number', 'Local AS Number', 'Peer IP Address', 'Local IP Address','MRTHeader']):
...                     r.write(line)

您的结果文件将如下所示：

$ cat results.txt
---------------------------------------------------
MRT Header
    Timestamp: 1453939200(2016-01-28 01:00:00)
    Peer AS Number: 37989
    Local AS Number: 12654
    Peer IP Address: 203.123.48.6
    Local IP Address: 193.0.4.28
---------------------------------------------------
MRT Header
    Timestamp: 1453939200(2016-01-28 01:00:00)
    Peer AS Number: 1836
    Local AS Number: 12654
    Peer IP Address: 146.228.1.3
    Local IP Address: 193.0.4.28
---------------------------------------------------