有没有一种方法可以从另一个文件中的一个文件中查找单词，并在新文件中输出在另一个文件中找不到的单词？

Question

I am trying to compare two files in Python, which both contain some words. I would like the code to look for words from file1 in file2 and put the words that are not found from file1 in a new file as an output.

The code below is what I've tried, but it doesn't do anything. It doesn't even show an error, so I don't know what goes wrong or should be different.

file1 = open('C:/Users/Atal/Desktop/School/Project datas/file1.txt')
file2 = open('C:/Users/Atal/Desktop/School/Project datas/file2.txt')

fileContent = file1.read();
fileContent2 = file2.read();

loglist = file1.readlines()

loglist2 = file2.readlines()
file2.close()

line = file1.readline()
file1.close()

found = False
for line in loglist:
if line in loglist2 :
    found = True

if not found:
file1 = open('C:/Users/Atal/Desktop/School/Project datas/file1.txt', 'w')
file1.write(line +"\n")
file1.close()

file1 looks like this: Peter Jan Richard

file2 looks like this: Floyd Richard Bob

The new file should look like this: Peter Jan

If there is any way to do this, please let me know. Thanks in advance.

Answer 1

Use set and not in like so:

list_1 = ['Peter', 'Jan', 'Richard']
list_2 = ['Floyd', 'Richard', 'Bob'] 

set_2 = set(list_2)  
main_list = [item for item in list_1 if item not in set_2]

main_list

Output:

['Peter', 'Jan']

Answer 2

When writing code, you need to keep in mind exactly what you're expecting each variable to contain at every step of your program's execution. For example, this:

loglist = file1.readlines()
...
line = file1.readline()
...
for line in loglist:

why do that middle statement at all, if you're just going to overwrite line immediately? And within your for loop:

for line in loglist:
    if line in loglist2:
        found = True

if not found:
    # save new file

So, if a line from loglist is found in loglist2 , then set the variable found to True . And if that didn't happen (if found remains False ) then output to file1. Note here that you're not doing anything else with line , and even if you were, the line file1.write(line +"\\n") only ever outputs one line and never repeats with other lines (or so I surmise from the way you indented your code in your question).

---

So, here's how you would do this more correctly. As you read through this, pay attention to what type (string, list, etc.) each variable is whenever it's used:

with open(".../file1.txt", "r") as file1, open(".../file2.txt", "r") as file2:
    logList1 = file1.readlines()
    logList2 = file2.readlines()
    # the with block will close the files automatically

for line in logList1:
    if line in logList2: 
        logList2.remove(line)  # if the line from file1 is found in file2, remove that line from file2

with open(".../file3.txt", "w") as file3:
    file3.writelines(logList2)  # write the contents of file2, after we removed lines from file1 from it

@johnny1995, in his answer, did the middle step in a list comprehension:

logList3 = [line for line in logList2 if line not in logList1]

which is essentially shorthand for what I did above: "make a new list containing every line from logList2 , but only if that line doesn't appear in logList1 ".