How to create list of duplicates of another list python

Question

The main problem is efficiency and creating dupes of dupes.

How to create file/list/any container with every duplicates from another list?

example inputs: 2 lists:

names = ['brian', 'adam', 'mickey', 'brian', 'mouse', 'barbara', 'mouse']

files = ['brian the wise', 'adam not interesting', 'mickey the fatty', 'brian intelligent', 'mouse notmikey', 'barbara smartie', 'mouse clicknotclik']

I tried method:

    for name in names:
        for j in range(len(names)):
            if not names.index(name)==j:
                if name == names[j]:
                    number = names.index(name)
                    a = open(title + ".txt", 'a')
                    a.write('\n' + str(files[number]) + str(files[j])+'\n')
                    a.close()

And it worked but not really efficient . I got output with duplicates.

The names and files types are lists.

Names contains one word and files contains this name and some data .

I need to find the same names (that's why I created another list called Names) in Names, when it finds it, it should create a txt with whole data from list files .

I know it's pretty complicated but I really tried to make my target clear.

Edit:

Alright, the desired output is:

brian the wise
brian the intelligent

mouse notmikey
mouse clicknotclik

When the real output is:

brian the wise
brian intelligent

brian the wise
brian intelligent

mouse notmikey
mouse clicknotclik

mouse notmikey
mouse clicknotclik

I know it's because it's checking the second Brian but i want this to write it just once if it found it.

Answer 1

You can do so with comprehension lists

This will try to see for each element of files if it contains at least one element from names .

The list(set()) clears duplicates

with open(title + '.txt', 'a') as f:
    [f.write("\n{}\n".format(entry)) for entry in files for name in list(set(names)) if name in entry] 

Without comprehension lists:

with open(title + '.txt', 'a') as f:
   for name in list(set(names)):
      for entry in files:
          f.write("\n{}\n".format(entry)) 

Answer 2

You can store all indexes of name into a dict and write to file only "information" duplicate entries:

names = ["brian", "adam", "mickey", "brian", "mickey", "mouse", "brian"]
files = ["brian the wise", "adam not interesting", "mickey the fatty", "brian intelligent",
         "mickey the creepy", "mouse notmikey", "brian the mad"]
title = "omg_what_a_weird_task"

with open(title + ".txt", "a") as f:
    tmp = {}
    for i, name in enumerate(names):
        if name not in tmp:
            tmp[name] = [i]
        else:
            tmp[name].append(i)
    for name, indexes in tmp.items():
        if len(indexes) > 1:
            f.write("\n".join(files[i] for i in indexes))
            f.write("\n")