How to write multiple output lines to a text file without overwriting previous multiple lines in python?

Question

Problem Statement:

Ubuntu 18.04 with python 3.6.9

1. python 3.6 script 'generator.py' keeps overwriting previous output lines in 'combined_output_file.txt'

2. 'Textgenerator.py' is the main script that imports 'generator' above which handles all open file reading (r) and writing (w+) functions.

python TextGenerator.py -t input_file_1.txt -c input_file_2.txt -o combined_output_file.txt

3. Contents of input_file_1.txt:
   This is line 1 of the FIRST input file.
   This is line 2 of the FIRST input file.
   This is line 3 of the FIRST input file.
   etc.

4. Contents of input_file_2.txt:

   This is line 1 of the SECOND input file.
   This is line 2 of the SECOND input file.
   This is line 3 of the SECOND input file.
   etc.

5. Correct output format for 'combined_output_file.txt'

This is line 1 of the FIRST input file.
This is line 1 of the SECOND input file.
1023 words generated via the gpt2 language model based on above lines... etc.

This is line 2 of the FIRST input file.
This is line 2 of the SECOND input file.
1023 NEW words generated via the gpt2 language model based on above lines... etc.

This is line 3 of the FIRST input file.
This is line 3 of the SECOND input file.
1023 MORE NEW words generated via the gpt2 language model based on above lines... etc.

6. Current overwritten output for 'combined_output_file.txt'

This is line 3 of the FIRST input file.
This is line 3 of the SECOND input file.
1023 words generated via the gpt2 language model based on above lines... etc.

Attempted solutions:

Switched w+ to a+ and added '\n' Same overwritten output as above.

def write_sample_to_file(self, filename, sample):
        """Write a given sample to a file specified by the filename."""
        with open(filename, 'a+', errors='surrogateescape', encoding='utf-8') as f:
            f.write(sample + '\n') # added and changed w+ to a+ same output  

how to write multiple lines in a file using python

Not sure if this is the correct approach. Can this be applied?

7. Required open, read, write, and generation def code blocks follow:

import os

from gpt2handler import Gpt2Handler ''' for model only '''

def generate_from_files(self,
                        title_filename,
                        content_filename=None,
                        num_samples=1,
                        print_output=False,
                        output_file=None,
                        num_words=1023):
    """Read the title from a file and initial content from another file then use gpt2 to generate an article
    and return it as a single string."""
    with open(title_filename, 'r', errors='surrogateescape') as title_file:
        for line in title_file: # added for 'input_file_1.txt'
            title = line # reading to end of input_file_1 but copying over each output line 1
        
    if content_filename:
        with open(content_filename, 'r', errors='surrogateescape') as content_file:
            for line in content_file: #added for 'input_file_1.txt'
                initial_content = line # reading to end of input_file_1 but copying over each output line 1
            
    else:
        initial_content = ''

    return self.generate(title, initial_content, num_samples, print_output, output_file, num_words)

def generate(self,
             title,
             initial_content=None,
             num_samples=1,
             print_output=False,
             output_file=None,
             num_words=1023):
    """Use gpt2 to generate an article based on a given title and initial content."""
    if not initial_content:
        initial_content = ''
    samples = Gpt2Handler.get_instance().generate_as_tuple(title, initial_content, num_samples, num_words)
    samples_str = [sample[0] + '\n' + sample[1] for sample in samples]

    if print_output:  # Print each article to the console is specified to
        for sample in samples_str:
            print(sample)
    if output_file:  # Write each of the samples to their own file if a base filename is specified
        self.write_samples_to_file(output_file, samples_str)
    
    return samples_str

def write_samples_to_file(self, filename, samples):
    """Write the given samples to a file. If there is more than one, write each to its own file."""
    if len(samples) == 1:
        self.write_sample_to_file(filename, samples[0]) 
    else:
        base, extension = os.path.splitext(filename)
        for i in range(len(samples)):
            new_filename = base + str(i) + extension
            self.write_sample_to_file(new_filename, samples[i])

def write_sample_to_file(self, filename, sample):
    """Write a given sample to a file specified by the filename."""
    with open(filename, 'w+', errors='surrogateescape', encoding='utf-8') as f:
        f.write(sample + '\n') # added and changed w+ to a+ same output

Answer 1

change

def write_sample_to_file(self, filename, sample):
    """Write a given sample to a file specified by the filename."""
    with open(filename, 'w+', errors='surrogateescape', encoding='utf-8') as f:
        f.write(sample + '\n') # added and changed w+ to a+ same output

to

def write_sample_to_file(self, filename, sample):
    """Write a given sample to a file specified by the filename."""
    with open(filename, 'a', errors='surrogateescape', encoding='utf-8') as f:
        f.write(sample + '\n') # added and changed w+ to a+ same output

You want to apprehend it with 'a' the file not write to it, for example if you did with open(index.html, w) it would check for a index.html in the same folder as your python file then if it found one delete it and create a new index.html and write whatever into it so you have to do with open(index.html, a) to look for an existing file and then add to it.