Mutliple output files created but empty - regex

Question

I am trying to split one file with two articles in it into two separate files with one article in each, for subsequent analysis of the articles. Each article in the initial file has an ID that I want to use to separate the files with, using RE.
Below is the initial input file, with ID number:
166068619 #### "Epilepsy: let's end our ignorance of this neglected condition
Helen Stephens is a young woman with epilepsy [...]."
106899978 #### "Great British Payoff shows that BBC governance is broken
If it was a television series, they'd probably call it [...]."
However, when I run my code, I do get two separate files as an output but they are empty.
This is my code:
def file_split(path_to_file):
"""Function splits bigger file into N smaller ones, based on a certain RE
match, that is used to break the bigger file into smaller ones"""
def pattern_extract(path_to_file):
"""Function identifies the number of RE occurences in a file,
No. can be used in further analysis as range No."""
import re
x = []
with open(path_to_file) as f:
for line in f:
match = re.search(r'^\d+?\t####\t', line)
if match:
a = match.group()
x.append(a)
return len(x)
y = pattern_extract(path_to_file)
m = y + 1
files = [open('filename%i.txt' %i, 'w') for i in range(1,m)]
with open(path_to_file) as f:
for line in f:
match = re.search(r'^\d+?\t####\t', line)
if match:
a = match.group()
#files = [open('filename%i.txt' %i, 'w') for i in range(1, m)]
files[i-1].write(a)
for f in files:
f.close()
return files
Output result is as follows:
file_split(path)
Out[19]:
[<open file 'filename1.txt', mode 'w' at 0x7fe121b130c0>,
<open file 'filename2.txt', mode 'w' at 0x7fe121b131e0>]
I am new to Python and I am not quite sure where the problem lies. I checked some other answers that addressed the multiple file outputs but cannot figure out the solution. Help would be very much appreciated.

Answer 1

There are two problems with your code:
you write only the line matching the ID (actually, just the match itself), not the rest
you are always writing to the last file, as you use i, the loop variable "left over" from the list comprehension
To fix it, you could change the lower portion of your code to this:
y = pattern_extract(path_to_file)
files = [open('filename%i.txt' %i, 'w') for i in range(y)]
n = -1
with open(path_to_file) as f:
for line in f:
if re.search(r'^\d+\s+####\s+', line):
n += 1
files[n].write(line)
But you do not have to read the file two times at all, just to count the matches: Just open another file when the line matches an ID line and directly write to that last file in the list, then close all the files.
open_files = []
with open(path_to_file) as f:
for line in f:
if re.search(r'^\d+\s+####\s+', line):
open_files.append(open('filename%d.txt' % len(open_files), 'w'))
open_files[-1].write(line)
for f in open_files:
f.close()