如何从文件中打印出与大文本文件中的输入字符串匹配的行？

Question

Here is my code my aim is to print a specific whole line from large text file where string equal to "SAMPLE TYPE" when i tried its printing in the object how to print specified line from whole file

import re
target = open("debug.txt", "r")
for line in target:
    search=re.search("[SAMPLE TYPE]",line)
    v1=search
    print v1

Gives output of:

None
None
None
None
None
<_sre.SRE_Match object at 0x7f870b7d5578>in this place instead of this i need to print the specifed line and i dont want the lines which doesnt contain specifed string.

My input file data:

HLS| 04/14/16 17:56:58:933 |hls_tsr_module.cpp|ReceiveData              |418 |DEBUG: Data copied to TSD from TSR is 0
HLS| 04/14/16 17:56:58:933 |mpm_h264.cpp   |FrameType                |1341|DEBUG: AU_DELIM NALU Unit Type
HLS| 04/14/16 17:56:58:933 |mpm_h264.cpp   |FrameType                |1341|DEBUG: SEI NALU Unit Type
HLS| 04/14/16 17:56:58:933 |mpm_h264.cpp   |FrameType                |1341|DEBUG: NON_IDR_PICTURE NALU Unit Type
HLS| 04/14/16 17:56:58:933 |mpm_h264.cpp   |FrameType                |1377|DEBUG: B Frame Received
HLS| 04/14/16 17:56:58:933 |hls_tsd_module.cpp|ProcessVideoBuffer       |4151|DEBUG: SAMPLE TYPE: B - FRAME PTS: 8573002542 DTS: 8573002542 
HLS| 04/14/16 17:56:58:933 |hls_tsd_module.cpp|ProcessVideoBuffer       |4193|DEBUG: Video send pts 8573002542
HLS| 04/14/16 17:56:58:933 |hls_tsm_module.cpp|AlternateFrameInterLeave |11770|DEBUG: Audio Record Status is 1
HLS| 04/14/16 17:56:58:934 |hls_tsd_module.cpp|ProcessVideoBuffer       |4261|DEBUG: Frame video pts 8573004043
HLS| 04/14/16 17:56:58:934 |hls_tsm_module.cpp|AlternateFrameInterLeave |11770|DEBUG: Audio Record Status is 1
HLS| 04/14/16 17:56:58:934 |hls_tsd_module.cpp|SegmentStream            |1597|DEBUG: Not an AV/Subtitle Packet 256
HLS| 04/14/16 17:56:58:934 |mpm_h264.cpp   |FrameType                |1341|DEBUG: AU_DELIM NALU Unit Type
HLS| 04/14/16 17:56:58:934 |mpm_h264.cpp   |FrameType                |1341|DEBUG: SEI NALU Unit Type
HLS| 04/14/16 17:56:58:934 |mpm_h264.cpp   |FrameType                |1341|DEBUG: NON_IDR_PICTURE NALU Unit Type
HLS| 04/14/16 17:56:58:934 |mpm_h264.cpp   |FrameType                |1377|DEBUG: B Frame Received
HLS| 04/14/16 17:56:58:934 |hls_tsd_module.cpp|ProcessVideoBuffer       |4151|DEBUG: SAMPLE TYPE: B - FRAME PTS: 8573004043 DTS: 8573004043 

Answer 1

import os
os.system('grep -rnw "[FOLDER_NAME]" -e "SEARCH_STRING" > OP.txt')

Answer 2

Python regex search method returns match object or None (if nothing is found). To get string from match object you need to call .group() .

In [1]: import re

In [2]: re.search("a", "aaa")
Out[2]: <_sre.SRE_Match at 0x7fe3514e98b8>

In [3]: re.search("a", "aaa").group()
Out[3]: 'a'

Check out the docs and this or this SO questions.

Answer 3

This is how it can be done:

with open("debug.txt", "r") as target:
    for line in target:
        if "[SAMPLE TYPE]" in line:
            print(line)

Note that I used the context manager (the with statement) for opening the file. Besides, no re is needed if you simply want to find a substring in another string.

Answer 4

Try:

if search:
    print(line)

The regular expression object that is being returned will evaluate to False when it can't find anything.

Answer 5

From the documentation : re.search returns a MatchObject instance. The documentation shows you how to access the searched for string, in your case for example with v1.group(0) .