在另一个主文本文件中搜索每个文本文件中的单词，如果使用python在主文件中找不到，则追加

Question

I need help on python code on below scenario.

I have two text files. one main file and one list file. Main file contains many words which i need to update when i found new word from list file.

I need to search each word of list file in main file. if any word not found in main file then i need to append that new word in main file.

i have code which will update file if string not found. but, i need to search each word from text file.

Main_File = "file path"
list_file="file path"

with open("Main_File", "r+") as file:
for line in file:
    if needle in line:
       break
else: # not found, we are at the eof
    file.write(needle) # append missing data
#this code will append if specific word not found in file.. but,i need to search each word from another file.

Answer 1

if word on your main file can be loaded in memory then you can load the words in set and check if the word is in main file like shown in sudo code below

main_file_words = set("load words from your main file".split())

list_file = # read list file
for word in list_file:
    if word not in main_file_words:
        main_file_words.add(word)
        list_file.write(word)

Answer 2

You could load the mainFile with mmap and search for the words from list file as follows:

import mmap

mainFilePath= "mainFile.txt"
listFilePath= "listFile.txt"
newWords=[]

# open main file with mmap
with open(mainFilePath, 'r') as mainFile:
    mainFileMmap = mmap.mmap(mainFile.fileno(), 0 , access=mmap.ACCESS_READ)

    # open list file and search for words in main file with mmap.find()
    with open(listFilePath, 'r') as listFile:
        for line in listFile:
            line= line.replace("\r", "").replace("\n", "") # remove line-feeds (quick and dirty)
            if mainFileMmap.find(line.encode()) == -1:
                newWords.append(line)

# append new words to main file
with open(mainFilePath, 'a') as mainFile:
    for newWord in set(newWords):
        mainFile.write("\n{}".format(newWord))