Question

Lets say I have a string that consists of x unknown chars. How could I get char nr. 13 or char nr. x-14?

Answer 1

First make sure the required number is a valid index for the string from beginning or end , then you can simply use array subscript notation.
use len(s) to get string length

>>> s = "python"
>>> s[3]
'h'
>>> s[6]
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
IndexError: string index out of range
>>> s[0]
'p'
>>> s[-1]
'n'
>>> s[-6]
'p'
>>> s[-7]
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
IndexError: string index out of range
>>>