Multiple queries for multiple input files

Question

I have developed a code to "capture" in several input.txt files those lines with a especific query, but now I would like to find several queries. For instance "find: AA or CD or BC" in the input file.

I have not found any way to do so. Any suggestion would be so helpful!

Input file

AA
AB
AC
CD
CD
AA
BC

Output file

AA
CD
CD
AA
BC

This is the code I am using now:

import fileinput
from collections import deque
output_file = 'output.txt' 
buscado = 'AA'

contexto = deque([], 4)  # for keeping the last 4 lines


with open(output_file, "w") as f_out:
    for line in fileinput.input(files=["input.txt", "input2.txt"]):
        contexto.append(line)       
        if len(contexto) < 4:      
            continue
        if buscado in contexto[1]:  
            f_out.writelines(contexto) 

Answer 1

You can do like this:

output_list = []
with open('data.txt', 'rt') as f:
    data = f.readlines()
for line in data:
    if line.strip('\n') in ("AA", "CD", "BC"):
        output_list.append(line.strip('\n'))
print(output_list)

Output:

['AA', 'CD', 'CD', 'AA', 'BC']

[EDIT] Using fileinput

If you want to use fileinput module to parse multiple files and to know in each file what keys are found it you can try like this:

import fileinput
 
with fileinput.FileInput(files=('data.txt', 'data1.txt'), mode='r') as input:
    for idx, line in enumerate(input):
        if input.isfirstline() == True:
            # Indicate the file name
            print(f'Reading file : {input.filename()}')
        if line.strip('\n') in ("AA", "CD", "BC"):
            print(line.strip('\n'))

Content of data.txt

AA
AB
AC
CD
CD
AA
BC

and

Content of data1.txt

AA
AB
AC
CD
CD
AA
BC
AA
BB
DD
FF
BC
BC

Output:

Reading file : data.txt
AA
CD
CD
AA
BC
Reading file : data1.txt
AA
CD
CD
AA
BC
AA
BC
BC