Remove amount of lines above and below a line containing a string

Question

I'm formatting GPS output logs and I need an efficient method to remove x number of lines above the line that contains a 0 and y number of lines below that line.

*--------------------------------------*
            UTC Time: 000000.00
           Latitude: 0000.0000
            N/S ind.: N
           Longitude: 0000.0000
         E/W ind: E
    Position fix ind: 0
     Satellites Used: 3
        MSL Altitude: 00.0
*--------------------------------------*

If the line contains "Position fix ind: 0", remove 6 lines above it and remove 3 lines below in and remove the line it is in

EDIT:

The input file is a .log file

EDIT 2:

input file

1
2
3
*--------------------------------------*
            UTC Time: 000000.00
           Latitude: 0000.0000
            N/S ind.: N
           Longitude: 0000.0000
         E/W ind: E
    Position fix ind: 0
     Satellites Used: 3
        MSL Altitude: 00.0
 *--------------------------------------*
3
2
1
1
2
3
*--------------------------------------*
            UTC Time: 000000.00
           Latitude: 0000.0000
            N/S ind.: N
           Longitude: 0000.0000
         E/W ind: E
    Position fix ind: 5
     Satellites Used: 3
        MSL Altitude: 00.0
*--------------------------------------*
3
2
1

Answer 1

I needed what @inspectorG4dget provided and for that I will extend my gratitude. But I needed to do the changes in 2500+ files and to the original files themself. I have added an extra function which handles that. The list.txt contains the name of files the changes are to be made to and the temp/tempfile is used for writing temporarily.

from shutil import copyfile

def remLines(infilepath, outfilepath, delim, above, below):
    infile = open(infilepath)
    outfile = open(outfilepath, 'w')
    buff = []
    line = infile.readline()
    while line:
        if line.strip() == delim:
            buff = []
            for _ in range(below):
                infile.readline() 
        else:
            if len(buff) == above:
                outfile.write(buff[0])
                buff = buff[1:]
            buff.append(line)
        line = infile.readline()
    outfile.write(''.join(buff))


def readfiles(listfilepath, tempfilepath):
    refile = open(listfilepath)
    line = refile.readline()
    while line:
        realfilepath = line.strip()
        remLines(realfilepath, tempfilepath, 'This is test line 17', 2,7)
        copyfile(tempfilepath, realfilepath)
        line = refile.readline()

if __name__ == "__main__":
    readfiles('list.txt', 'temp/tempfile')

Answer 2

You can use a set here, iterate over the file and as soon as you see 'Position fix ind: 0' in a line(say, index of the line is i), then add a set of numbers from i-6 to i+3 to a set.

f = open('abc')
se = set()
for i,x in enumerate(f):
    if 'Position fix ind: 0' in x:
        se.update(range(i-6,i+4))
f.close()

Now iterate over the file again and skip those indexes that are present in that set:

f = open('abc')
f1 = open('out.txt', 'w')
for i,x in enumerate(f):
    if i not in se:
        f1.write(x)
f.close()
f1.cose()

input file:

1
2
3
*--------------------------------------*
            UTC Time: 000000.00
           Latitude: 0000.0000
            N/S ind.: N
           Longitude: 0000.0000
         E/W ind: E
    Position fix ind: 0
     Satellites Used: 3
        MSL Altitude: 00.0
 *--------------------------------------*
3
2
1
1
2
3
*--------------------------------------*
            UTC Time: 000000.00
           Latitude: 0000.0000
            N/S ind.: N
           Longitude: 0000.0000
         E/W ind: E
    Position fix ind: 5
     Satellites Used: 3
        MSL Altitude: 00.0
*--------------------------------------*
3
2
1

output:

1
2
3
3
2
1
1
2
3
*--------------------------------------*
UTC Time: 000000.00
Latitude: 0000.0000
N/S ind.: N
Longitude: 0000.0000
E/W ind: E
Position fix ind: 5
Satellites Used: 3
MSL Altitude: 00.0
*--------------------------------------*
3
2
1

Answer 3

def remLines(infilepath, outfilepath, delim, above, below):
    infile = open(infilepath)
    outfile = open(outfilepath, 'w')
    buff = []
    line = infile.readline()
    while line:
        if line.strip() == delim:
             buff = []
             for _ in range(below): # need to error check here, if you're not certain that your input file is correctly formatted
                 infile.readline()
        else:
            if len(buff) == above:
                outfile.write(buff[0])
                buff = buff[1:]
            buff.append(line)
        line = infile.readline()
    outfile.write(''.join(buff))

if __name__ == "__main__":
    remLines('path/to/input', 'path/to/output', "Position fix ind: 0", 6,3)

Testing:

Input:

1
2
3
*--------------------------------------*
            UTC Time: 000000.00
           Latitude: 0000.0000
            N/S ind.: N
           Longitude: 0000.0000
         E/W ind: E
    Position fix ind: 0
     Satellites Used: 3
        MSL Altitude: 00.0
 *--------------------------------------*
3
2
1
1
2
3
*--------------------------------------*
            UTC Time: 000000.00
           Latitude: 0000.0000
            N/S ind.: N
           Longitude: 0000.0000
         E/W ind: E
    Position fix ind: 5
     Satellites Used: 3
        MSL Altitude: 00.0
*--------------------------------------*
3
2
1

Output:

1
2
3
3
2
1
1
2
3
*--------------------------------------*
            UTC Time: 000000.00
           Latitude: 0000.0000
            N/S ind.: N
           Longitude: 0000.0000
         E/W ind: E
    Position fix ind: 5
     Satellites Used: 3
        MSL Altitude: 00.0
*--------------------------------------*
3
2
1

Answer 4

If the files aren't too large:

 import re
 p = re.compile(r'(?:.*\n){6}\s*Position fix ind: 0\n(?:.*\n){3}')
 with open('test.txt') as f:
    output = p.sub('', f.read())