How to only read lines in a text file after a certain string?

Use a boolean to ignore lines up to that point:

found_abstract = False
for files in filepath:
    with open(files, 'r') as f:
        for line in f:
            if 'Abstract' in line:
                found_abstract = True
            if found_abstract:
                #do whatever you want

Just start another loop when you reach the line you want to start from:

for files in filepath:
    with open(files, 'r') as f:
        for line in f:
            if 'Abstract' in line:                
                for line in f: # now you are at the lines you want
                    # do work

A file object is its own iterator, so when we reach the line with 'Abstract' in it we continue our iteration from that line until we have consumed the iterator.

A simple example:

gen = (n for n in xrange(8))

for x in gen:
    if x == 3:
        print('Starting second loop')
        for x in gen:
            print('In second loop', x)
    else:
        print('In first loop', x)

Produces:

In first loop 0
In first loop 1
In first loop 2
Starting second loop
In second loop 4
In second loop 5
In second loop 6
In second loop 7

You can also use itertools.dropwhile to consume the lines up to the point you want:

from itertools import dropwhile

for files in filepath:
    with open(files, 'r') as f:
        dropped = dropwhile(lambda _line: 'Abstract' not in _line, f)
        next(dropped, '')
        for line in dropped:
                print(line)