如何在python中比较和合并两个文件

我有两个文本文件，名称是 one.txt 和 Two.txt 在 one.txt 中，内容是

AAA
BBB
CCC
DDD

在two.txt中，内容是

DDD
EEE

我想要一个Python代码来确定one.txt中是否存在two.txt的包含 如果存在意味着不执行任何操作，但是如果two.txt 的内容不存在意味着它应该附加到one.txt

我想要 one.txt 中的输出为

AAA
BBB
CCC
DDD
EEE

Code:

file1 = open("file1.txt", "r") 
file2 = open("file2.txt", "r") 
file3 = open("resultss.txt", "w") 
list1 = file1.readlines() 
list2 = file2.readlines() 
file3.write("here: \n") 
for i in list1: for j in list2: 
   if i==j: file3.write(i)

这很简单sets https://docs.python.org/2.7/library/stdtypes.html#set-types-set-frozenset，因为它会为您处理重复项

Edit

with open('file1.txt',"a+") as file1, open('file2.txt') as file2:
    new_words = set(file2) - set(file1)
    if new_words:
        file1.write('\n') #just in case, we don't want to mix to words together 
        for w in new_words:
            file1.write(w)

Edit 2

如果顺序很重要，请选择 Max Chretien 的答案。

如果你想知道常用词，可以使用交集

with open('file1.txt',"a+") as file1, open('file2.txt') as file2:
    words1 = set(file1)
    words2 = set(file2)
    new_words = words2 - words1
    common = words1.intersection(words2)
    if new_words:
        file1.write('\n')
        for w in new_words:
            file1.write(w)
    if common:
        print 'the commons words are'
        print common
    else:
        print 'there are no common words'