python 寻找两个文件相同字符段并写入新的文件

Question

fd = {}
 
for l in open('a.txt', 'r'):
    ar = l.split(' ')
    fd[ar[0]] = ar[0]
 
with open('output.txt', 'w') as fw:
    for l in open('b.txt', 'r'):
        ar = l.strip()
        ar = l.split(' ')
        #print(len(ar))
        for i in range (len(ar)):
            if ar[i] in fd:
                fw.write(ar[0] + " " + ar[i]+ "\n")
        

为什么明明在array的元素找不到？也就是有几个ar[i]本来在fd里却说不在，导致output少了几行

Answer 1

a.txt和b.txt的么文件内容是什么？

 

        for i in range (len(ar)):

            if ar[0] in fd: #应该用ar[0]吧

                fw.write(ar[0] + " " + ar[i]+ "\n")