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pythonregextext
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Reputation: 1857

Parsing big text file using regex

I have a huge text file (1 GB), where each "line" is separated by ##.
For example:

## sentence 1 ## sentence 2
## sentence 3

I'm trying to print the file according to the ## separation.

I tried the following code, but the read() function crush (because the size of the file).

import re

dataFile = open('post.txt', 'r')
p = re.compile('##(.+)')

iterator = p.finditer(dataFile.read())
for match in iterator:
    print (match.group())

dataFile.close()

Any ideas?

Upvotes: 2

Views: 409

Answers (2)

Vaibhav Aggarwal
Vaibhav Aggarwal

Reputation: 1411

You can use islice.

from itertools import islice

file = open('file.txt', 'r')
while True:
  slice = islice(file, buffer)
  to_process = []
  for line in slice:
    to_process.append(line)
  if not to_process:
    break
  #process to_process list
file.close()

buffer is the number of lines you want to read at a time (you have to define the int).

Upvotes: 1

unutbu
unutbu

Reputation: 879113

This will read the file in chunks (of chunksize bytes) thus avoiding memory issues related to reading too much of the file all at once:

import re
def open_delimited(filename, delimiter, *args, **kwargs):
    """
    http://stackoverflow.com/a/17508761/190597
    """
    with open(filename, *args, **kwargs) as infile:
        chunksize = 10000
        remainder = ''
        for chunk in iter(lambda: infile.read(chunksize), ''):
            pieces = re.split(delimiter, remainder + chunk)
            for piece in pieces[:-1]:
                yield piece
            remainder = pieces[-1]
        if remainder:
            yield remainder

filename = 'post.txt'
for chunk in open_delimited(filename, '##', 'r'):
    print(chunk)
    print('-'*80)

Upvotes: 4

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