iterating over files

[buran]

please, show what your CONFIG.inp file looks like and what the expected output is (one file)
did you check configparser module and can you use it? i.e. is your file compatible with a format that configparser can read?

---

names = ['b','c','d','e']
with open('CONFIG.inp') as f:
    current_config = f.read()
for i, name in enumerate(names, start=1):
    new_config = current_config.replace('a', name)
    with open(f'COFIG{i}.inp', 'w') as f:
        f.write(new_config)

untested, but should work for python 3.6+