Записать все совпадающие компоненты файлов A и B в файл С

def to_normal(input_array): # убираем дубликаты слов, все слова -> в 1 список
    normal_array = []
    for line in input_array:
        for word in line:
            if word not in normal_array:
                normal_array.append(word)
    return(normal_array)
    
f1 = open('text_01.txt','r')
f2 = open('text_02.txt','r')
f_res = open('text_res.txt','w')
 
f1_array = [word.split() for word in f1]
f2_array = [word.split() for word in f2]
f1_array_01 = to_normal(f1_array)
f2_array_01 = to_normal(f2_array)
 
flag_count=0
for word_01 in f1_array_01:
    for word_02 in f2_array_01:
        if word_01 == word_02:
            f_res.write(word_01 + ' ')
            flag_count+=1
if flag_count == 0:
    f_res.write('No coincidence, sorry man')
 
f_res.close()
f2.close()
f1.close()

f1 = open('text_01.txt')
f2 = open('text_02.txt')
f3 = open('text_result.txt','w')
f1_array = [line.split() for line in f1]
f2_array = [line.split() for line in f2]
f1_set, f2_set = set(), set()
for f1_str in f1_array:
    f1_set=f1_set|set(f1_str)
for f2_str in f2_array:
    f2_set=f2_set|set(f2_str)
f3_set=f1_set & f2_set    
f3.write(str(f3_set))
f3.close()

from itertools import chain
 
def words(fname):
    with  open(fname, "rt", encoding="utf-8") as f:
        return chain(*(line.split() for line in f))
 
f1_set = set(words("text_01.txt"))
f2_set = set(words("text_02.txt"))
 
with open("text_result.txt", "wt", encoding="utf-8") as f:
    for word in f1_set & f2_set:
        print(word, file=f)