CODEWITHSUNDEEP
pythonpython-3.xfile-handling
Ankur
Ankur

Reputation: 477

Python Not able to append new line character after the end of a line when writing to a new file?

In below method I am sorting the contents of the file according to timestamp , and it's working fine also But I don't know how to append new line when I am writing to a newly made file.It is writing in the same line I want to change the lines in my output file as input is very large I need to use chunk in this case so using readlines or storing in any data structure will won't work here

1)My Input file format is as below

TIME[04.26_12:30:30:853664]  ID[ROLL:201987623]  MARKS[PHY:100|MATH:200|CHEM:400]
TIME[03.27_12:29:30.553669]  ID[ROLL:201987623]  MARKS[PHY:100|MATH:1200|CHEM:900]
TIME[03.26_12:28:30.753664]  ID[ROLL:2341987623] MARKS[PHY:100|MATH:200|CHEM:400]
TIME[03.26_12:29:30.853664]  ID[ROLL:201978623]  MARKS[PHY:0|MATH:0|CHEM:40]
TIME[04.27_12:29:30.553664]  ID[ROLL:2034287623] MARKS[PHY:100|MATH:200|CHEM:400]

Code is as below

import re
from functools import partial
from itertools import groupby
from typing import Tuple

regex = re.compile(r"^.*TIME\[([^]]+)\]ID\[ROLL:([^]]+)\].+$")
def func1(arg) -> bool:
    return regex.match(arg)


def func2(arg) -> Tuple[str, int]:
    match = regex.match(arg)
    if match:
        return match.group(1), int(match.group(2))
    return "", 0

def func3(arg) -> int:
    match = regex.match(arg)
    if match:
        return int(match.group(2))
    return 0

def read_in_chunks(file_object, chunk_size=1024*1024):
    while True:
        data = file_object.read(chunk_size)
        if not data:
            break
        yield data

with open('b.txt') as fr:
    for chunk in read_in_chunks(fr):
        collection = filter(func1, chunk.splitlines())
        collection = sorted(collection, key=func2)
        for key, group in groupby(collection, key=func3):
            with open(f"ROLL_{key}", mode="wa") as fw:
                fw.writelines(group)# want suggestions to append newline character before every line

2)Actual Output what I am getting now

In file name ROLL_201987623.txt

 TIME[03.27_12:29:30.553669]  ID[ROLL:201987623]  MARKS[PHY:100|MATH:1200|CHEM:900]  TIME[04.26_12:30:30:853664]  ID[ROLL:201987623]  MARKS[PHY:100|MATH:200|CHEM:400]

3)Desired Output (I want to change the line as given in input format)

 TIME[03.27_12:29:30.553669]  ID[ROLL:201987623]  MARKS[PHY:100|MATH:1200|CHEM:900]  
 TIME[04.26_12:30:30:853664]  ID[ROLL:201987623]  MARKS[PHY:100|MATH:200|CHEM:400]

Currently I am getting the output in the same line that is the main problem for me ?

Upvotes: 0

Views: 149

Answers (2)

mousetail 'he-him'
mousetail 'he-him'

Reputation: 8001

The writelines() function, despite its name, will not actually add a newline character to each line. (this is done to correspond with .readlines() function that will not remove the \ \n in the file.

I would suggest using fw.writelines([i+'\n' for i in group]) to manually add the necessary line breaks.

Upvotes: 1

Shivam Jha
Shivam Jha

Reputation: 4462

Maybe this will help:

#  suggestions to append newline character before every line
group = map(lambda x: x + '\n', group)
fw.writelines(group)

Upvotes: 1

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