Concatenating files in order

[Mahmood Naderan]

Hi,
There are some text files ending with _chunk_i where 'i' is an integer. For example,

XXX_chunk_0
XXX_chunk_1
...

I want to concatenate them in order. Thing is that the total number of files may be variable. Therefore, I can not specify the number in my python script. It has to be "for all files ending with _chunk_i".

Next, I can write

with open('final.txt', 'w') as outf:
for fname in filenames:
            with open(fname) as inf:
                for line in inf:
        outf.write(line)
 

How can I specify the "filenames"?
Regards,
Mahmood