'int' object is not subscriptable

[lateublegende]

my code

line = line.strip()
            except AttributeError:
                line = line
            line+1    
            lines = open("T:\donne\donne.txt").read().splitlines()
            lines.append([1])
            lines=line
            lines= int(linestowrite)
            open("T:\donne\donne.txt",'w').write((lines[1]).join(lines))
            break

my error

Error:
Traceback (most recent call last):
  File "Z:\programmepython\ssh2.py", line 49, in <module>
    open("T:\donne\donne.txt",'w').write((lines[1]).join(lines))
TypeError: 'int' object is not subscriptable

how I fix that? my var is all defined. I use python 3.7.1