Extract Values between two strings in a text file using python

Question

Lets say I have a Text file with the below content

fdsjhgjhg
fdshkjhk
Start
Good Morning
Hello World
End
dashjkhjk
dsfjkhk

Now I need to wr

Answer 1

Using itertools.dropwhile, itertools.takewhile, itertools.islice:

import itertools

with open('data.txt') as f, open('result.txt', 'w') as fout:
    it = itertools.dropwhile(lambda line: line.strip() != 'Start', f)
    it = itertools.islice(it, 1, None)
    it = itertools.takewhile(lambda line: line.strip() != 'End', it)
    fout.writelines(it)

UPDATE: As inspectorG4dget commented, above code copies over the first block. To copy multiple blocks, use following:

import itertools

with open('data.txt', 'r') as f, open('result.txt', 'w') as fout:
    while True:
        it = itertools.dropwhile(lambda line: line.strip() != 'Start', f)
        if next(it, None) is None: break
        fout.writelines(itertools.takewhile(lambda line: line.strip() != 'End', it))

Answer 2

Just in case you have multiple "Start"s and "End"s in your text file, this will import all the data together, excluding all the "Start"s and "End"s.

with open('path/to/input') as infile, open('path/to/output', 'w') as outfile:
    copy = False
    for line in infile:
        if line.strip() == "Start":
            copy = True
            continue
        elif line.strip() == "End":
            copy = False
            continue
        elif copy:
            outfile.write(line)

Answer 3

If the text files aren't necessarily large, you can get the whole content of the file then use regular expressions:

import re
with open('data.txt') as myfile:
    content = myfile.read()

text = re.search(r'Start\n.*?End', content, re.DOTALL).group()
with open("result.txt", "w") as myfile2:
    myfile2.write(text)

Answer 4

I'm not a Python expert, but this code should do the job.

inFile = open("data.txt")
outFile = open("result.txt", "w")
keepCurrentSet = False
for line in inFile:
    if line.startswith("End"):
        keepCurrentSet = False

    if keepCurrentSet:
        outFile.write(line)

    if line.startswith("Start"):
        keepCurrentSet = True
inFile.close()
outFile.close()

Answer 5

import re

inFile = open("data.txt")
outFile = open("result.txt", "w")
buffer1 = ""
keepCurrentSet = True
for line in inFile:
    buffer1=buffer1+(line)

buffer1=re.findall(r"(?<=Start) (.*?) (?=End)", buffer1)  
outFile.write("".join(buffer1))  
inFile.close()
outFile.close()

Answer 6

Move the outFile.write call into the 2nd if:

inFile = open("data.txt")
outFile = open("result.txt", "w")
buffer = []
for line in inFile:
    if line.startswith("Start"):
        buffer = ['']
    elif line.startswith("End"):
        outFile.write("".join(buffer))
        buffer = []
    elif buffer:
        buffer.append(line)
inFile.close()
outFile.close()