Try the method rstrip() (see doc Python 2 and Python 3)
>>> 'test string\n'.rstrip()
'test string'
Python's rstrip() method strips all kinds of trailing whitespace by default, not just one newline as Perl does with chomp.
>>> 'test string \n \r\n\n\r \n\n'.rstrip()
'test string'
To strip only newlines:
>>> 'test string \n \r\n\n\r \n\n'.rstrip('\n')
'test string \n \r\n\n\r '
There are also the methods strip(), lstrip() and strip():
>>> s = " \n\r\n \n abc def \n\r\n \n "
>>> s.strip()
'abc def'
>>> s.lstrip()
'abc def \n\r\n \n '
>>> s.rstrip()
' \n\r\n \n abc def'