TypeError: 'str' does not support the buffer interface in python

You're running a python 2 script with python 3. Python 3 now returns bytes no longer str when reading from a binary stream.

3 choices:

1. run it with python 2. That if you don't have the rights/time to adapt the script, not recommended as python 3 is becoming more and more the norm.

2. change your code to insert a decode function (it will continue to work in python 2):

username = cred_file.readlines()[0].decode().split(';')[0]

If file is opened in read/binary mode, readlines returns a list of bytes not str. You have do decode the bytes into a str to apply str methods.

3. open the file in "r" instead of "rb". readlines then returns a list of str and your code will work. Sometimes it can be problematic on windows because of need to preserve the carriage return (\r) chars, so look out for side effects in your code.

Note: cred_file.readlines()[0] is a questionable construction: you're reading the whole file lines, and drop all the lines but the first. Not very efficient I/O and CPU wise. Prefer that: cred_file.readline() which is equivalent to read the first line. If you need to read all the lines for further processing, then store the result of readlines in a list.