How to concatenate files while looping through lists?

[python_newbie09]

I have a few hundreds of files in one folder and every file in the folder has 2 more corresponding files that it needs to combine with. I have done the code for finding the corresponding files and adding them into a list but I am now stuck at figuring out how to combine these files while looping through each list.

f = f = ['a_b_c_111.hdf', 'b_b_c_111.hdf', 'b_c_e_112.hdf','c_c_e_112.hdf']
file_to_combine = {}

for file in f:
    a,b,c,d = re.split(r'[_]',file)
    s = c + '_' + d
    if s in file_to_combine:        
        file_to_combine[s].append(os.path.join(file))
    else:
        file_to_combine[s] =[os.path.join(file)]

for (k, v) in file_to_combine.items():    
    files = [','.join(v)]
    
    for i in files:
        split_files = files[0].split(",")
        print (split_files) 

running this script will result in 2 lists but it will be more when I run through 100s of files:

['a_b_c_111.hdf', 'b_b_c_111.hdf']
['b_c_e_112.hdf', 'c_c_e_112.hdf']

I am now stuck and finding a way to loop through this list and concatenating hdf files within each of this list.
Would appreciate some help on how best to do this. Thanks.