Python - Write multiple files data to master file

File handling is an important part of any web application.

Python has several functions for creating, reading, updating, and deleting files.

To write to an existing file, you must add a parameter to the open()function −

"a" − Append − will append to the end of the file

"w" − Write − will overwrite any existing content

Example

import os # list the files in directory lis = os.listdir('D:\python' '\data_files\data_files') print(lis) tgt = os.listdir('D:\python' '\data_files\target_file')   file_dir ='D:\python\data_files\data_files' out_file = r'D:\python\data_files\target_file\master.txt' ct = 0   print('target file :', tgt) try:    # check for if file exists    # if yes delete the file    # otherwise data will be appended to existing file    if len(tgt)>0:       os.remove('D:\python' '\data_files\target_file\master.txt')       open(tgt, 'a').close()    else:       # create an empty file       open(tgt, 'a').close() except:    head = open('D:\python' '\data_files\target_file\master.txt', 'a+')    line ='empno, ename, sal'    # write header to output    print(head, line)    head.close()    # below loop to write data to output file    for line1 in lis:       f_dir = file_dir+'\'+line1       # open files in read mode       in_file = open(f_dir, 'r+')       # open output in append mode       w = open(out_file, 'a+')       d = in_file.readline()       d = in_file.readlines()       w.write("\n")       for line2 in d:          print(line2)          w.write(line2)           ct = ct + 1      w.close()       #using pandas import pandas as pd # pd.read_csv creates dataframes df1 = pd.read_csv('D:\python\data_files\data_files\emp_1.txt') df2 = pd.read_csv('D:\python\data_files\data_files\emp_2.txt') df3 = pd.read_csv('D:\python\data_files\data_files\emp_3.txt') frames = [df1, df2, df3] # concat function concatenates the frames result = pd.concat(frames) # to_csv function writes output to file result.to_csv('D:\python\data_files' '\target_file\master.txt', encoding ='utf-8', index = False)